> On May 19, 2011, 7:34 a.m., Aaron J. Seigo wrote: > > those are some impressive results. my guess is that we likely have a very > > similar issue in plasma. in both cases, we are dealing with lots of small > > bits of memory in the form of pixmaps, strings, etc. that are fairly > > constantly coming and going. switching between compositing and no > > compositing is probably the 'worst case' real world scenario for this. > > > > if this does test out well, i'd suggest putting this code in libkworkspace > > so that all of our apps with this usage pattern (plasma-desktop, > > plasma-netbook, krunner, kwin, ..) can take advantage of a common > > implementation. a set of static methods in the KWorkspace namespace should > > suffice. > > > > if you could repeat your experiment with plasma-desktop with and without > > such a patch, that would be great and let us know whether we should adopt > > such a strategy across the plasma shell components. > > > > as for portability ... i'm not overly concerned about the portability of > > this to non-glibc systems as those systems are our primary targets. > > however, instead of checking for GLIBC the code could simply check for > > M_TRIM_THRESHOLD. for comparison, here is how busybox does this same trick > > for both the trim size and mmap request size threshold: > > > > #ifndef PAGE_SIZE > > # define PAGE_SIZE (4*1024) /* guess */ > > #endif > > #ifdef M_TRIM_THRESHOLD > > /* M_TRIM_THRESHOLD is the maximum amount of freed top-most memory > > * to keep before releasing to the OS > > * Default is way too big: 256k > > */ > > mallopt(M_TRIM_THRESHOLD, 2 * PAGE_SIZE); > > #endif > > #ifdef M_MMAP_THRESHOLD > > /* M_MMAP_THRESHOLD is the request size threshold for using mmap() > > * Default is too big: 256k > > */ > > mallopt(M_MMAP_THRESHOLD, 8 * PAGE_SIZE - 256); > > #endif > > > > i doubt we need to tweak the mmap strategy, but i like the checks for the > > definitions of mallopt there. for portability to non-unix-y systems, we > > could wrap this whole thing in a #ifndef Q_WS_WIN block which should keep > > the KDE Windows team from pulling their hair out over the use of such > > UNIX-y API ;)
sysconf(_SC_PAGESIZE) returns the page size for mmap, no need for (4*1024) - Ivan ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: http://git.reviewboard.kde.org/r/101385/#review3402 ----------------------------------------------------------- On May 18, 2011, 8:53 p.m., Philipp Knechtges wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > http://git.reviewboard.kde.org/r/101385/ > ----------------------------------------------------------- > > (Updated May 18, 2011, 8:53 p.m.) > > > Review request for kwin and Plasma. > > > Summary > ------- > > The intention of this patch is to lower the heap fragmentation in KWin when > using the raster backend. > > One can illustrate the issue with the following testcase: If one currently > uses the raster backend and > switches back to non-compositing mode one gets easily a similar memory usage > like the following: > > Situation: 14 windows, QtCurve > KWin started with compositing: 40 MB > KWin switched to non-compositing : more than 70 MB > > The first guess might be, that this is due to a memleak because of not > properly released pixmaps. > But calling malloc_stats() sheds some more light on the subject > (non-compositing mode): > > Arena 0: > system bytes = 72232960 > in use bytes = 8180512 > Arena 1: > system bytes = 135168 > in use bytes = 4784 > Total (incl. mmap): > system bytes = 73080832 > in use bytes = 8898000 > max mmap regions = 13 > max mmap bytes = 36343808 > > In other words, the glibc has allocated more than 70 MB memory although KWin > uses only less than 10 MB. > The problem is that glibc only resizes the heap if the heap has more than 128 > KB of free space at the end, but > many decoration pixmaps are smaller. Using mallopt to tune the threshold to > 20 KB (i'm open for other suggestions?) > fixes the issue. After the patch: > > KWin in compositing mode: 19 MB > KWin switched to non-compositing: 13 MB > > > Arena 0: > system bytes = 12374016 > in use bytes = 6894544 > Arena 1: > system bytes = 135168 > in use bytes = 4784 > Total (incl. mmap): > system bytes = 13750272 > in use bytes = 8140416 > max mmap regions = 67 > max mmap bytes = 99463168 > > Are there some negative effects? > The only negative effect i am aware of is, that Glibc free() is calling the > sbrk syscall more often. But this should > not be a bottleneck. > > > Diffs > ----- > > kwin/composite.cpp 9edb99d > kwin/main.cpp f767f54 > > Diff: http://git.reviewboard.kde.org/r/101385/diff > > > Testing > ------- > > Tested using a standard Fedora 14. > Would be nice to know, whether other OSes have similar issues? > Martin Gräßlin had some concerns about the portability? > > > Thanks, > > Philipp > >
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