> From: Minchan Kim [mailto:minchan@xxxxxxxxxx] > Subject: Re: zram /proc/swaps accounting weirdness > > 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. Agreed. > > 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? I also cannot reproduce it with only zram, without zcache. I can only reproduce with zcache+zram. Since zcache will only "fall through" to zram when the frontswap_store() call in swap_writepage() fails, I wonder if in both cases swap_writepage() is being called in large (e.g. SWAPFILE_CLUSTER-sized) blocks of pages? When zram-only, the entire block of pages always gets sent to zram, but with zcache only a small randomly-positioned fraction fail frontswap_store(), but the SWAPFILE_CLUSTER-sized blocks have already been pre-reserved on the swap device and become only partially-filled? Thanks, Dan -- 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