Many thanks Minchan. On Thu, May 25, 2017 at 9:06 PM, Minchan Kim <minchan@xxxxxxxxxx> wrote: > If it is swap cache hit, it's not a major fault which causes IO > so VM count it as minor fault, not major. Cool---but see below. > Yub, I expected you guys used zram with readahead off so it shouldn't > be a big problem. By the way, I was referring to page clustering. We do this in sysctl.conf: # Disable swap read-ahead vm.page-cluster = 0 I figured that the readahead from the disk device (/sys/block/zram0/queue/read_ahead_kb) is not meaningful---am I correct? These numbers are from a Chromebook with a few dozen Chrome tabs and a couple of Android apps, and pretty heavy use of zram. pgpgin 4688863 pgpgout 442052 pswpin 353675 pswpout 1072021 ... pgfault 5564247 pgmajfault 355758 pgmajfault_s 6297 pgmajfault_a 317645 pgmajfault_f 31816 pgmajfault_ax 8494 pgmajfault_fx 13201 where _s, _a, and _f are for shmem, anon, and file pages. (ax and fx are for the subset of executable pages---I was curious about that) So the numbers don't completely match: anon faults = 318,000 swap ins = 354,000 Any idea of what might explain the difference? > About auto resetting readahead with zram, I agree with you. > But there are some reasons I postpone the work. No want to discuss > it in this thread/moment. ;) Yes, I wasn't even thinking of auto-resetting, just log a warning. >> Incidentally, I understand anon and file faults, but what's a shmem fault? > > For me, it was out of my interest but if you want to count shmem fault, > maybe, we need to introdue new stat(e.g., PSWPIN_SHM) in shmem_swapin > but there are concrete reasons to justify in changelog. :) Actually mine was a simpler question---I have no idea what a major shmem fault is. And for this experiment it's a relatively small number, but a similar order of magnitude to the (expensive) file faults, so I don't want to completely ignore it. Thanks again. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
