urllib2 performance on windows, usb connection
I've googled this pretty extensively and can't find anyone who's had the same problem, so here it is: I wrote a console program in python to download podcasts, so speed is an issue. I have 1.6 M down. The key bit of downloading code is this: source = urllib2.urlopen( url ) target = open( filename, 'wb' ) target.write( source.read() ) This runs great on Ubuntu. I get DL speeds of about 1.5 Mb/s on the SATA HD or on a usb-connected iPod, but if I run the same program on Windows (with a 2 GHz core 2 duo, 7200 rpm sata drive---better hardware specs than the Ubuntu box), it maxes out at about 500 kb/s. Worse, if I DL directly to my iPod in disk mode, I'm lucky if I even hit 100 kb/s. So does anyone know what the deal is with this? Why is the same code so much slower on Windows? Hope someone can tell me before a holy war erupts :-) --danny -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 performance on windows, usb connection
Martin v. Löwis wrote: So does anyone know what the deal is with this? Why is the same code so much slower on Windows? Hope someone can tell me before a holy war erupts :-) Only the holy war can give an answer here. It certainly has *nothing* to do with Python; Python calls the operating system functions to read from the network and write to the disk almost directly. So it must be the operating system itself that slows it down. To investigate further, you might drop the write operating, and measure only source.read(). If that is slower, then, for some reason, the network speed is bad on Windows. Maybe you have the network interfaces misconfigured? Maybe you are using wireless on Windows, but cable on Linux? Maybe you have some network filtering software running on Windows? Maybe it's just that Windows sucks?-) If the network read speed is fine, but writing slows down, I ask the same questions. Perhaps you have some virus scanner installed that filters all write operations? Maybe Windows sucks? Regards, Martin Thanks for the ideas, Martin. I ran a couple of experiments to find the culprit, by downloading the same 20 MB file from the same fast server. I compared: 1. DL to HD vs USB iPod. 2. AV on-access protection on vs. off 3. "source. read()" only vs. "file.write( source.read() )" The culprit is definitely the write speed on the iPod. That is, everything runs plenty fast (~1 MB/s down) as long as I'm not writing directly to the iPod. This is kind of odd, because if I copy the file over from the HD to the iPod using windows (drag-n-drop), it takes about a second or two, so about 10 MB/s. So the problem is definitely partially Windows, but it also seems that Python's file.write() function is not without blame. It's the combination of Windows, iPod and Python's data stream that is slowing me down. I'm not really sure what I can do about this. I'll experiment a little more and see if there's any way around this bottleneck. If anyone has run into a problem like this, I'd love to hear about it... thanks again, --danny -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 performance on windows, usb connection
MRAB wrote: dq wrote: > Martin v. Löwis wrote: >>> So does anyone know what the deal is with this? Why is the same code so >>> much slower on Windows? Hope someone can tell me before a holy war >>> erupts :-) >> >> Only the holy war can give an answer here. It certainly has *nothing* to >> do with Python; Python calls the operating system functions to read from >> the network and write to the disk almost directly. So it must be the >> operating system itself that slows it down. >> >> To investigate further, you might drop the write operating, and measure >> only source.read(). If that is slower, then, for some reason, the >> network speed is bad on Windows. Maybe you have the network interfaces >> misconfigured? Maybe you are using wireless on Windows, but cable on >> Linux? Maybe you have some network filtering software running on >> Windows? Maybe it's just that Windows sucks?-) >> >> If the network read speed is fine, but writing slows down, I ask the >> same questions. Perhaps you have some virus scanner installed that >> filters all write operations? Maybe Windows sucks? >> >> Regards, >> Martin >> > > Thanks for the ideas, Martin. I ran a couple of experiments to find the > culprit, by downloading the same 20 MB file from the same fast server. I > compared: > > 1. DL to HD vs USB iPod. > 2. AV on-access protection on vs. off > 3. "source. read()" only vs. "file.write( source.read() )" > > The culprit is definitely the write speed on the iPod. That is, > everything runs plenty fast (~1 MB/s down) as long as I'm not writing > directly to the iPod. This is kind of odd, because if I copy the file > over from the HD to the iPod using windows (drag-n-drop), it takes about > a second or two, so about 10 MB/s. > > So the problem is definitely partially Windows, but it also seems that > Python's file.write() function is not without blame. It's the > combination of Windows, iPod and Python's data stream that is slowing me > down. > > I'm not really sure what I can do about this. I'll experiment a little > more and see if there's any way around this bottleneck. If anyone has > run into a problem like this, I'd love to hear about it... > You could try copying the file to the iPod using the command line, or copying data from disk to iPod in, say, C, anything but Python. This would allow you to identify whether Python itself has anything to do with it. Well, I think I've partially identified the problem. target.write( source.read() ) runs perfectly fast, copies 20 megs in about a second, from HD to iPod. However, if I run the same code in a while loop, using a certain block size, say target.write( source.read(4096) ), it takes forever (or at least I'm still timing it while I write this post). The mismatch seems to be between urllib2's block size and the write speed of the iPod, I might try to tweak this a little in the code and see if it has any effect. Oh, there we go: 20 megs in 135.8 seconds. Yeah... I might want to try to improve that... -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 performance on windows, usb connection
dq wrote: MRAB wrote: dq wrote: > Martin v. Löwis wrote: >>> So does anyone know what the deal is with this? Why is the same code so >>> much slower on Windows? Hope someone can tell me before a holy war >>> erupts :-) >> >> Only the holy war can give an answer here. It certainly has *nothing* to >> do with Python; Python calls the operating system functions to read from >> the network and write to the disk almost directly. So it must be the >> operating system itself that slows it down. >> >> To investigate further, you might drop the write operating, and measure >> only source.read(). If that is slower, then, for some reason, the >> network speed is bad on Windows. Maybe you have the network interfaces >> misconfigured? Maybe you are using wireless on Windows, but cable on >> Linux? Maybe you have some network filtering software running on >> Windows? Maybe it's just that Windows sucks?-) >> >> If the network read speed is fine, but writing slows down, I ask the >> same questions. Perhaps you have some virus scanner installed that >> filters all write operations? Maybe Windows sucks? >> >> Regards, >> Martin >> > > Thanks for the ideas, Martin. I ran a couple of experiments to find the > culprit, by downloading the same 20 MB file from the same fast server. I > compared: > > 1. DL to HD vs USB iPod. > 2. AV on-access protection on vs. off > 3. "source. read()" only vs. "file.write( source.read() )" > > The culprit is definitely the write speed on the iPod. That is, > everything runs plenty fast (~1 MB/s down) as long as I'm not writing > directly to the iPod. This is kind of odd, because if I copy the file > over from the HD to the iPod using windows (drag-n-drop), it takes about > a second or two, so about 10 MB/s. > > So the problem is definitely partially Windows, but it also seems that > Python's file.write() function is not without blame. It's the > combination of Windows, iPod and Python's data stream that is slowing me > down. > > I'm not really sure what I can do about this. I'll experiment a little > more and see if there's any way around this bottleneck. If anyone has > run into a problem like this, I'd love to hear about it... > You could try copying the file to the iPod using the command line, or copying data from disk to iPod in, say, C, anything but Python. This would allow you to identify whether Python itself has anything to do with it. Well, I think I've partially identified the problem. target.write( source.read() ) runs perfectly fast, copies 20 megs in about a second, from HD to iPod. However, if I run the same code in a while loop, using a certain block size, say target.write( source.read(4096) ), it takes forever (or at least I'm still timing it while I write this post). The mismatch seems to be between urllib2's block size and the write speed of the iPod, I might try to tweak this a little in the code and see if it has any effect. Oh, there we go: 20 megs in 135.8 seconds. Yeah... I might want to try to improve that... After some tweaking of the block size, I managed to get the DL speed up to about 900 Mb/s. It's still not quite Ubuntu, but it's a good order of magnitude better. The new DL code is pretty much this: """ blocksize = 2 ** 16# plus or minus a power of 2 source = urllib2.urlopen( 'url://string' ) target = open( pathname, 'wb') fullsize = float( source.info()['Content-Length'] ) DLd = 0 while DLd < fullsize: DLd = DLd + blocksize # optional: write some DL progress info # somewhere, e.g. stdout target.close() source.close() """ -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 performance on windows, usb connection
MRAB wrote: dq wrote: MRAB wrote: dq wrote: Martin v. Löwis wrote: So does anyone know what the deal is with this? Why is the same code so much slower on Windows? Hope someone can tell me before a holy war erupts :-) Only the holy war can give an answer here. It certainly has *nothing* to do with Python; Python calls the operating system functions to read from the network and write to the disk almost directly. So it must be the operating system itself that slows it down. To investigate further, you might drop the write operating, and measure only source.read(). If that is slower, then, for some reason, the network speed is bad on Windows. Maybe you have the network interfaces misconfigured? Maybe you are using wireless on Windows, but cable on Linux? Maybe you have some network filtering software running on Windows? Maybe it's just that Windows sucks?-) If the network read speed is fine, but writing slows down, I ask the same questions. Perhaps you have some virus scanner installed that filters all write operations? Maybe Windows sucks? Thanks for the ideas, Martin. I ran a couple of experiments to find the culprit, by downloading the same 20 MB file from the same fast server. I compared: 1. DL to HD vs USB iPod. 2. AV on-access protection on vs. off 3. "source. read()" only vs. "file.write( source.read() )" The culprit is definitely the write speed on the iPod. That is, everything runs plenty fast (~1 MB/s down) as long as I'm not writing directly to the iPod. This is kind of odd, because if I copy the file over from the HD to the iPod using windows (drag-n-drop), it takes about a second or two, so about 10 MB/s. So the problem is definitely partially Windows, but it also seems that Python's file.write() function is not without blame. It's the combination of Windows, iPod and Python's data stream that is slowing me down. I'm not really sure what I can do about this. I'll experiment a little more and see if there's any way around this bottleneck. If anyone has run into a problem like this, I'd love to hear about it... You could try copying the file to the iPod using the command line, or copying data from disk to iPod in, say, C, anything but Python. This would allow you to identify whether Python itself has anything to do with it. Well, I think I've partially identified the problem. target.write( source.read() ) runs perfectly fast, copies 20 megs in about a second, from HD to iPod. However, if I run the same code in a while loop, using a certain block size, say target.write( source.read(4096) ), it takes forever (or at least I'm still timing it while I write this post). The mismatch seems to be between urllib2's block size and the write speed of the iPod, I might try to tweak this a little in the code and see if it has any effect. Oh, there we go: 20 megs in 135.8 seconds. Yeah... I might want to try to improve that... How long does it take to transfer 4KB? If it can transfer 1MB/s then I'd say that 4KB is too small. Generally speaking, the higher the data rate, the larger the blocks you should be transferring at a time, IMHO. You could write a script to test the transfer speed with different block sizes. Thanks MRAB, 32 or 64 KB seems to be quickest, but I'll do a more scientific test soon and see what turns up. -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 performance on windows, usb connection
MRAB wrote: dq wrote: dq wrote: MRAB wrote: dq wrote: Martin v. Löwis wrote: So does anyone know what the deal is with this? Why is the same code so much slower on Windows? Hope someone can tell me before a holy war erupts :-) Only the holy war can give an answer here. It certainly has *nothing* to do with Python; Python calls the operating system functions to read from the network and write to the disk almost directly. So it must be the operating system itself that slows it down. To investigate further, you might drop the write operating, and measure only source.read(). If that is slower, then, for some reason, the network speed is bad on Windows. Maybe you have the network interfaces misconfigured? Maybe you are using wireless on Windows, but cable on Linux? Maybe you have some network filtering software running on Windows? Maybe it's just that Windows sucks?-) If the network read speed is fine, but writing slows down, I ask the same questions. Perhaps you have some virus scanner installed that filters all write operations? Maybe Windows sucks? Regards, Martin Thanks for the ideas, Martin. I ran a couple of experiments to find the culprit, by downloading the same 20 MB file from the same fast server. I compared: 1. DL to HD vs USB iPod. 2. AV on-access protection on vs. off 3. "source. read()" only vs. "file.write( source.read() )" The culprit is definitely the write speed on the iPod. That is, everything runs plenty fast (~1 MB/s down) as long as I'm not writing directly to the iPod. This is kind of odd, because if I copy the file over from the HD to the iPod using windows (drag-n-drop), it takes about a second or two, so about 10 MB/s. So the problem is definitely partially Windows, but it also seems that Python's file.write() function is not without blame. It's the combination of Windows, iPod and Python's data stream that is slowing me down. I'm not really sure what I can do about this. I'll experiment a little more and see if there's any way around this bottleneck. If anyone has run into a problem like this, I'd love to hear about it... You could try copying the file to the iPod using the command line, or copying data from disk to iPod in, say, C, anything but Python. This would allow you to identify whether Python itself has anything to do with it. Well, I think I've partially identified the problem. target.write( source.read() ) runs perfectly fast, copies 20 megs in about a second, from HD to iPod. However, if I run the same code in a while loop, using a certain block size, say target.write( source.read(4096) ), it takes forever (or at least I'm still timing it while I write this post). The mismatch seems to be between urllib2's block size and the write speed of the iPod, I might try to tweak this a little in the code and see if it has any effect. Oh, there we go: 20 megs in 135.8 seconds. Yeah... I might want to try to improve that... After some tweaking of the block size, I managed to get the DL speed up to about 900 Mb/s. It's still not quite Ubuntu, but it's a good order of magnitude better. The new DL code is pretty much this: """ blocksize = 2 ** 16# plus or minus a power of 2 source = urllib2.urlopen( 'url://string' ) target = open( pathname, 'wb') fullsize = float( source.info()['Content-Length'] ) DLd = 0 while DLd < fullsize: DLd = DLd + blocksize # optional: write some DL progress info # somewhere, e.g. stdout target.close() source.close() """ I'd like to suggest that the block size you add to 'DLd' be the actual size of the returned block, just in case the read() doesn't return all you asked for (it might not be guaranteed, and the chances are that the final block will be shorter, unless 'fullsize' happens to be a multiple of 'blocksize'). If less is returned by read() then the while-loop might finish before all the data has been downloaded, and if you just add 'blocksize' each time it might end up > 'fullsize', ie apparently >100% downloaded! Interesting. I'll if to see if any of the downloaded files end prematurely :) btw, I forgot the most important line of the code! """ blocksize = 2 ** 16# plus or minus a power of 2 source = urllib2.urlopen( 'url://string' ) target = open( pathname, 'wb') fullsize = float( source.info()['Content-Length'] ) DLd = 0 while DLd < fullsize: # +++ target.write( source.read( blocksize ) ) # +++ # +++ DLd = DLd + blocksize # optional: write some DL progress info # somewhere, e.g. stdout target.close() source.close() """ Using that, I'm not quite sure where I can grab onto the value of how much was actually re
Re: urllib2 performance on windows, usb connection
MRAB wrote: dq wrote: MRAB wrote: dq wrote: dq wrote: MRAB wrote: dq wrote: Martin v. Löwis wrote: So does anyone know what the deal is with this? Why is the same code so much slower on Windows? Hope someone can tell me before a holy war erupts :-) Only the holy war can give an answer here. It certainly has *nothing* to do with Python; Python calls the operating system functions to read from the network and write to the disk almost directly. So it must be the operating system itself that slows it down. To investigate further, you might drop the write operating, and measure only source.read(). If that is slower, then, for some reason, the network speed is bad on Windows. Maybe you have the network interfaces misconfigured? Maybe you are using wireless on Windows, but cable on Linux? Maybe you have some network filtering software running on Windows? Maybe it's just that Windows sucks?-) If the network read speed is fine, but writing slows down, I ask the same questions. Perhaps you have some virus scanner installed that filters all write operations? Maybe Windows sucks? Regards, Martin Thanks for the ideas, Martin. I ran a couple of experiments to find the culprit, by downloading the same 20 MB file from the same fast server. I compared: 1. DL to HD vs USB iPod. 2. AV on-access protection on vs. off 3. "source. read()" only vs. "file.write( source.read() )" The culprit is definitely the write speed on the iPod. That is, everything runs plenty fast (~1 MB/s down) as long as I'm not writing directly to the iPod. This is kind of odd, because if I copy the file over from the HD to the iPod using windows (drag-n-drop), it takes about a second or two, so about 10 MB/s. So the problem is definitely partially Windows, but it also seems that Python's file.write() function is not without blame. It's the combination of Windows, iPod and Python's data stream that is slowing me down. I'm not really sure what I can do about this. I'll experiment a little more and see if there's any way around this bottleneck. If anyone has run into a problem like this, I'd love to hear about it... You could try copying the file to the iPod using the command line, or copying data from disk to iPod in, say, C, anything but Python. This would allow you to identify whether Python itself has anything to do with it. Well, I think I've partially identified the problem. target.write( source.read() ) runs perfectly fast, copies 20 megs in about a second, from HD to iPod. However, if I run the same code in a while loop, using a certain block size, say target.write( source.read(4096) ), it takes forever (or at least I'm still timing it while I write this post). The mismatch seems to be between urllib2's block size and the write speed of the iPod, I might try to tweak this a little in the code and see if it has any effect. Oh, there we go: 20 megs in 135.8 seconds. Yeah... I might want to try to improve that... After some tweaking of the block size, I managed to get the DL speed up to about 900 Mb/s. It's still not quite Ubuntu, but it's a good order of magnitude better. The new DL code is pretty much this: """ blocksize = 2 ** 16# plus or minus a power of 2 source = urllib2.urlopen( 'url://string' ) target = open( pathname, 'wb') fullsize = float( source.info()['Content-Length'] ) DLd = 0 while DLd < fullsize: DLd = DLd + blocksize # optional: write some DL progress info # somewhere, e.g. stdout target.close() source.close() """ I'd like to suggest that the block size you add to 'DLd' be the actual size of the returned block, just in case the read() doesn't return all you asked for (it might not be guaranteed, and the chances are that the final block will be shorter, unless 'fullsize' happens to be a multiple of 'blocksize'). If less is returned by read() then the while-loop might finish before all the data has been downloaded, and if you just add 'blocksize' each time it might end up > 'fullsize', ie apparently >100% downloaded! Interesting. I'll if to see if any of the downloaded files end prematurely :) btw, I forgot the most important line of the code! """ blocksize = 2 ** 16# plus or minus a power of 2 source = urllib2.urlopen( 'url://string' ) target = open( pathname, 'wb') fullsize = float( source.info()['Content-Length'] ) DLd = 0 while DLd < fullsize: # +++ target.write( source.read( blocksize ) ) # +++ # +++ DLd = DLd + blocksize # optional: write some DL progress info # somewhere, e.g. stdout target.close() source.close() """ Using that, I'm not quite sure where I can grab onto the value of ho
