> From: Minchan Kim [mailto:minchan@xxxxxxxxxx] > Sent: Thursday, November 22, 2012 10:52 PM > To: Luigi Semenzato > Cc: linux-mm@xxxxxxxxx; Dan Magenheimer > Subject: Re: behavior of zram stats, and zram allocation limit > > On Wed, Nov 21, 2012 at 02:58:48PM -0800, Luigi Semenzato wrote: > > Hi, > > > > Two questions for zram developers/users. (Please let me know if it is > > NOT acceptable to use this list for these questions.) > > > > 1. When I run a synthetic load using zram from kernel 3.4.0, > > compr_data_size from /sys/block/zram0 seems to decrease even though > > orig_data_size stays constant (see below). Is this a bug that was > > fixed in a later release? (The synthetic load is a bunch of processes > > that allocate memory, fill half of it with data from /dev/urandom, and > > touch the memory randomly.) I looked at the code and it looks right. > > :-P > > > > 2. Is there a way of setting the max amount of RAM that zram is > > allowed to allocate? Right now I can set the size of the > > *uncompressed* swap device, but how much memory gets allocated depends > > on the compression ratio, which could vary. > > There is no method to limit the RAM size but I think we can implement > it easily. The only thing we need is just a "voice of customer". > Why do you need it? Hi Minchan -- I am not an expert on zram, but I do recall a conversation with hughd in 2010 along this line and, after some thought, he concluded it was far harder than it sounds. Since zram appears as a block device, it is not easy to reject writes. Zcache circumvents the block I/O system entirely so "writes" can be managed much more dynamically. 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