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b=E21ryJ6k7ZRC/x3HnIYXKjJb8pZyISGJTauG+sNaEBXAExCjFbvq8Ui3wU6cMAA8+ YaFn3EfkB6+DhJY6nhHVFyHBh9whFH1Tc6iFrCat1alfztO0ZRsl7chen+QtrA8vM5 +7igdmHey2TR56QjM2S+WASF+UoSZvf0usAupuL3SzbxsJSPt/tQNcmSPDTR4l9/KC DjjJRSKW8UvGi8tklxTvI/yi5ZyIB82PZl7hzk7I7Wz/Pb8W4Ochw04j3iepVTUbX6 uvOay1rKPnsPbvBytSwn7/LqFmUlUlLkYcC5Dv4tOIvgeXAVhLzZgLQ9g+/+woepcd Ai4KLYdxajk7g== Message-ID: Date: Fri, 10 Jul 2026 11:54:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: extract __free_to_pcs_batch() from free_to_pcs_bulk() Content-Language: en-US To: Hao Li Cc: Harry Yoo , Andrew Morton , Shengming Hu , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260707-slab-simplify-bulk-pcs-v1-1-4850dbe0d904@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4ACB840005 X-Stat-Signature: rheh6sb5fc4xrn5sdbngbnq7x3rxrg49 X-HE-Tag: 1783677290-463995 X-HE-Meta: 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 gnn/Yy6+ 8LmXXQlPtWDoXPXiWsjQFOh1iM7veu/T/BiHRuijYcZ0UYheoKu0g2Eoecq+uWa2Izcr70aJsK5qnxs6JsIrSEAiiHhP2HmzC38S9/A67arCyjyrtxsNT0OQmnEuS8zVNI3SNABUEXKvEvfiNRQ72crdlwoMi3hmuVpJIGvNgPXWgRcB3pynep2+7eH47xRx8jnx3arYmYX3JdWoYPr8Qth64Ly9BiMk6CTcRKbBXRg92DbEsFds2TO9eloLJKx18jhkZxOtPPXeV/WIzQp2PYmZewUphxRcQ3wci5tkNywk91fFNXBAR0ro33dqrm1AMRTroPNymTwdqL2o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/10/26 07:21, Hao Li wrote: > On Fri, Jul 10, 2026 at 01:18:25PM +0800, Hao Li wrote: >> On Tue, Jul 07, 2026 at 02:16:00PM +0200, Vlastimil Babka (SUSE) wrote: >> > It has been noted that free_to_pcs_bulk() is difficult to follow, with a >> > number of goto labels, and this has contributed to two memory leak bugs >> > in there. >> > >> > Extract part of the code to __free_to_pcs_batch(), which focuses only on >> > freeing free-hook-processed local objects to a percpu sheaf, and >> > returning how many were freed. Zero means a trylock failure or no empty >> > sheaf available, and thus the caller should fallback to >> > __kmem_cache_free_bulk(). >> > >> > Make free_to_pcs_bulk() call this in a while loop, removing all goto >> > labels from the function. __free_to_pcs_batch() retains two rather >> > straightforward ones. >> > >> > Signed-off-by: Vlastimil Babka (SUSE) >> >> Nice simplification! >> >> [...] >> > +/* >> > + * Bulk free objects to the percpu sheaves. >> > + * Unlike free_to_pcs() this includes the calls to all necessary hooks >> > + * and the fallback to freeing to slab pages. >> > + */ >> > +static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p) >> > +{ >> > + bool init = slab_want_init_on_free(s); >> > + void *remote_objects[PCS_BATCH_MAX]; >> > + unsigned int remote_nr = 0; >> > + >> > + for (unsigned int i = 0; i < size;) { >> > + struct slab *slab = virt_to_slab(p[i]); >> > + >> > + memcg_slab_free_hook(s, slab, p + i, 1); >> > + alloc_tagging_slab_free_hook(s, slab, p + i, 1); >> > + >> > + if (unlikely(!slab_free_hook(s, p[i], init, false))) { >> > + p[i] = p[--size]; >> > + continue; >> > + } >> > + >> > + if (unlikely(!can_free_to_pcs(slab))) { >> > + remote_objects[remote_nr] = p[i]; >> > + p[i] = p[--size]; >> > + if (++remote_nr >= PCS_BATCH_MAX) { >> > + __kmem_cache_free_bulk(s, remote_nr, &remote_objects[0]); >> > + stat_add(s, FREE_SLOWPATH, remote_nr); >> > + remote_nr = 0; >> > + } >> > + continue; >> > + } >> > + >> > + i++; >> > } >> > >> > - if (remote_nr) >> > - goto flush_remote; >> > + while (size) { >> > + unsigned int batch_freed = __free_to_pcs_batch(s, size, p); >> > >> > - return; >> > + if (!batch_freed) >> > + break; >> > >> > -no_empty: >> > - local_unlock(&s->cpu_sheaves->lock); >> > + p += batch_freed; >> > + size -= batch_freed; >> > + } >> > >> > - /* >> > - * if we depleted all empty sheaves in the barn or there are too >> > - * many full sheaves, free the rest to slab pages >> > - */ >> > -fallback: >> > - __kmem_cache_free_bulk(s, size, p); >> > - stat_add(s, FREE_SLOWPATH, size); >> > + if (size) { >> > + __kmem_cache_free_bulk(s, size, p); >> > + stat_add(s, FREE_SLOWPATH, size); >> > + } >> >> By the way, could we move this directly into the loop inside the >> `if (!batch_freed)` block to make it a bit more concise? but it's totally fine >> to leave it as is! :) Ah right, great suggestion! will do. > oops, forgot to add the r-b tag just now :P > > Reviewed-by: Hao Li Thanks! >> >> > >> > -flush_remote: >> > if (remote_nr) { >> > __kmem_cache_free_bulk(s, remote_nr, &remote_objects[0]); >> > stat_add(s, FREE_SLOWPATH, remote_nr); >> > >> > --- >> > base-commit: 72bb229f9161a1efcd5df32141b69fcc6ae81a13 >> > change-id: 20260707-slab-simplify-bulk-pcs-a8d0478feef6 >> > >> > Best regards, >> > -- >> > Vlastimil Babka (SUSE) >> > >