> -----Original Message----- > From: Johannes Weiner <hannes@xxxxxxxxxxx> > Sent: Thursday, September 26, 2024 11:43 AM > To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx> > Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > linux-mm@xxxxxxxxx; nphamcs@xxxxxxxxx; chengming.zhou@xxxxxxxxx; > usamaarif642@xxxxxxxxx; shakeel.butt@xxxxxxxxx; ryan.roberts@xxxxxxx; > Huang, Ying <ying.huang@xxxxxxxxx>; 21cnbao@xxxxxxxxx; akpm@linux- > foundation.org; Zou, Nanhai <nanhai.zou@xxxxxxxxx>; Feghali, Wajdi K > <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh <vinodh.gopal@xxxxxxxxx> > Subject: Re: [PATCH v7 6/8] mm: zswap: Support mTHP swapout in > zswap_store(). > > On Thu, Sep 26, 2024 at 05:29:30PM +0000, Sridhar, Kanchana P wrote: > > > > 3) Keep the approach in v7 where obj_cgroup_get/put is localized to > > > > zswap_store_page for both success and error conditions, and any > > > unwinding > > > > state in zswap_store will take care of dropping references obtained > from > > > > prior successful writes (from this or prior invocations of zswap_store). > > > > > > I am also fine with doing that and doing the reference batching as a follow > up. > > > > I think so too! We could try and improve upon (3) with reference batching > > in a follow-up patch. > > Yeah, I agree. The percpu-refcounts are not that expensive, we should > be able to live with per-page ops for now. > > One thing you *can* do from the start is tryget a pool reference in > zswap_store(), to prevent the pools untimely demise while you work on > it, and then in zswap_store_page() you can do gets instead of trygets. Sure, this sounds good Johannes, thanks for the suggestion! I already do a zswap_pool_current_get() at the beginning of zswap_store in the v7 code, for this purpose. > > You'd have to rename zswap_pool_get() to zswap_pool_tryget() (which is > probably for the best) and implement the trivial new zswap_pool_get(). Ok, will do so. Thanks, Kanchana
