On Tue, Oct 1, 2024 at 10:01 AM Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx> wrote: > > > -----Original Message----- > > From: Johannes Weiner <hannes@xxxxxxxxxxx> > > Sent: Tuesday, October 1, 2024 4:11 AM > > To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx> > > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; > > yosryahmed@xxxxxxxxxx; nphamcs@xxxxxxxxx; > > chengming.zhou@xxxxxxxxx; usamaarif642@xxxxxxxxx; > > shakeel.butt@xxxxxxxxx; ryan.roberts@xxxxxxx; Huang, Ying > > <ying.huang@xxxxxxxxx>; 21cnbao@xxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; > > willy@xxxxxxxxxxxxx; Zou, Nanhai <nanhai.zou@xxxxxxxxx>; Feghali, Wajdi K > > <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh <vinodh.gopal@xxxxxxxxx> > > Subject: Re: [PATCH v10 6/7] mm: zswap: Support large folios in > > zswap_store(). > > > > On Mon, Sep 30, 2024 at 10:32:21PM -0700, Kanchana P Sridhar wrote: > > > zswap_store() will store large folios by compressing them page by page. > > > > > > This patch provides a sequential implementation of storing a large folio > > > in zswap_store() by iterating through each page in the folio to compress > > > and store it in the zswap zpool. > > > > > > zswap_store() calls the newly added zswap_store_page() function for each > > > page in the folio. zswap_store_page() handles compressing and storing each > > > page. > > > > > > We check the global and per-cgroup limits once at the beginning of > > > zswap_store(), and only check that the limit is not reached yet. This is > > > racy and inaccurate, but it should be sufficient for now. We also obtain > > > initial references to the relevant objcg and pool to guarantee that > > > subsequent references can be acquired by zswap_store_page(). A new > > function > > > zswap_pool_get() is added to facilitate this. > > > > > > If these one-time checks pass, we compress the pages of the folio, while > > > maintaining a running count of compressed bytes for all the folio's pages. > > > If all pages are successfully compressed and stored, we do the cgroup > > > zswap charging with the total compressed bytes, and batch update the > > > zswap_stored_pages atomic/zswpout event stats with folio_nr_pages() > > once, > > > before returning from zswap_store(). > > > > > > If an error is encountered during the store of any page in the folio, > > > all pages in that folio currently stored in zswap will be invalidated. > > > Thus, a folio is either entirely stored in zswap, or entirely not stored > > > in zswap. > > > > > > The most important value provided by this patch is it enables swapping out > > > large folios to zswap without splitting them. Furthermore, it batches some > > > operations while doing so (cgroup charging, stats updates). > > > > > > This patch also forms the basis for building compress batching of pages in > > > a large folio in zswap_store() by compressing up to say, 8 pages of the > > > folio in parallel in hardware using the Intel In-Memory Analytics > > > Accelerator (Intel IAA). > > > > > > This change reuses and adapts the functionality in Ryan Roberts' RFC > > > patch [1]: > > > > > > "[RFC,v1] mm: zswap: Store large folios without splitting" > > > > > > [1] https://lore.kernel.org/linux-mm/20231019110543.3284654-1- > > ryan.roberts@xxxxxxx/T/#u > > > > > > Co-developed-by: Ryan Roberts > > > > I would change that to > > > > Originally-by: Ryan Roberts <ryan.roberts@xxxxxxx> > > > > > Signed-off-by: > > > > and drop this for now. > > Thanks Johannes. Sure, this sounds good. Should I post a v11 for just this > specific patch which this change, or a v11 for the entire series? Andrew could probably make the change for you while applying the patches to mm-unstable if you ask nicely :) Also since we agreed further cleanup can be done as a followup: Acked-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
