hi guys i have /var and swap on an SD card (sandisk class4 4GB) in an embedded network device, which turns out to be reeeeally slow. System under certain circumstances freezes and in top i see iowait at 90% and processes which touch sd card, like kswapd, kjournald and *mmc*d are all on io-wait (D)
i found some help at linaro for sorting out if it is the SD card, which most probably is and try now to search a card which is fast enough but tried also to sort out if maybe it is the kernel, because something is fishy there. can you guys help me a little on that? the card is a high-speed card, but it is not running in highspeed mode: cat /sys/kernel/debug/mmc0/ios clock: 25000000 Hz vdd: 20 (3.2 ~ 3.3 V) bus mode: 2 (push-pull) chip select: 0 (don't care) power mode: 2 (on) bus width: 2 (4 bits) timing spec: 0 (legacy) i then forced the card setting to highspeed mode (by commenting out some returns in mmc_switch_hs() and found out that the card meets all requirements for highspeed, but card->sw_caps.hs_max_dtr is 0 is that value the maximum bus speed which the card can handle? i assume when it is 0 it means it is limited to legacy specifications, which is quite slow (?) or is it regardless for performance if a SDHC card runs in legacy mode? thank you in advance kind regards, peter -- :: e n d i a n :: open source - open minds :: peter warasin :: http://www.endian.com :: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
