> From: Dan Magenheimer > Sent: Wednesday, October 12, 2011 2:39 PM > To: Seth Jennings; gregkh@xxxxxxx > Cc: cascardo@xxxxxxxxxxxxxx; rdunlap@xxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; rcj@xxxxxxxxxxxxxxxxxx; brking@xxxxxxxxxxxxxxxxxx > Subject: RE: [PATCH] staging: zcache: remove zcache_direct_reclaim_lock > > > From: Seth Jennings [mailto:sjenning@xxxxxxxxxxxxxxxxxx] > > Subject: [PATCH] staging: zcache: remove zcache_direct_reclaim_lock > > > > zcache_do_preload() currently does a spin_trylock() on the > > zcache_direct_reclaim_lock. Holding this lock intends to prevent > > shrink_zcache_memory() from evicting zbud pages as a result > > of a preload. > > > > However, it also prevents two threads from > > executing zcache_do_preload() at the same time. The first > > thread will obtain the lock and the second thread's spin_trylock() > > will fail (an aborted preload) causing the page to be either lost > > (cleancache) or pushed out to the swap device (frontswap). It > > also doesn't ensure that the call to shrink_zcache_memory() is > > on the same thread as the call to zcache_do_preload(). > > Yes, this looks to be leftover code from early in kztmem/zcache > development. Good analysis. > > > Additional, there is no need for this mechanism because all > > zcache_do_preload() calls that come down from cleancache already > > have PF_MEMALLOC set in the process flags which prevents > > direct reclaim in the memory manager. If the zcache_do_preload() > > Might it be worthwhile to add a BUG/ASSERT for the presence > of PF_MEMALLOC, or at least a comment in the code? > > > call is done from the frontswap path, we _want_ reclaim to be > > done (which it isn't right now). > > > > This patch removes the zcache_direct_reclaim_lock and related > > statistics in zcache. > > > > Based on v3.1-rc8 > > > > Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> > > Reviewed-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> > > With added code/comment per above... > Acked-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> After Seth's further analysis, ignore my conditional and consider v1 of this patch: Acked-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href