Hi Dan, On Fri, Dec 07, 2012 at 03:57:08PM -0800, Dan Magenheimer wrote: > While playing around with zcache+zram (see separate thread), > I was watching stats with "watch -d". > > It appears from the code that /sys/block/num_writes only > increases, never decreases. In my test, num_writes got up Never decreasement is natural. > to 1863. /sys/block/disksize is 104857600. > > I have two swap disks, one zram (pri=60), one real (pri=-1), > and as a I watched /proc/swaps, the "Used" field grew rapidly > and reached the Size (102396k) of the zram swap, and then > the second swap disk (a physical disk partition) started being > used. Then for awhile, the Used field for both swap devices > was changing (up and down). > > Can you explain how this could happen if num_writes never > exceeded 1863? This may be harmless in the case where Odd. I tried to reproduce it with zram and real swap device without zcache but failed. Does the problem happen only if enabling zcache together? > the only swap on the system is zram; or may indicate a bug > somewhere? > > It looks like num_writes is counting bio's not pages... > which would imply the bio's are potentially quite large > (and I'll guess they are of size SWAPFILE_CLUSTER which is > defined to be 256). Do large clusters make sense with zram? Swap_writepage handles a page and zram_make_request doesn't use pluging mechanism of block I/O. So every request for swap-over-zram is a bio and a page. So your problem might be a BUG. > > Late on a Friday so sorry if I am incomprehensible... > > P.S. The corresponding stat for zcache indicates that > it failed 8852 stores, so I would have expected zram > to deal with no more than 8852 compressions. > > -- > 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> -- Kind regards, Minchan Kim -- 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>