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Howlett" , Christoph Lameter , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org References: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> <20250214-slub-percpu-caches-v2-7-88592ee0966a@suse.cz> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 661032118B X-Spam-Score: -3.01 X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[google.com,oracle.com,linux.com,linux.dev,gmail.com,kvack.org,vger.kernel.org,lists.infradead.org]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On 2/25/25 09:54, Harry Yoo wrote: > On Fri, Feb 14, 2025 at 05:27:43PM +0100, Vlastimil Babka wrote: >> The possibility of many barn operations is determined by the current >> number of full or empty sheaves. Taking the barn->lock just to find out >> that e.g. there are no empty sheaves results in unnecessary overhead and >> lock contention. Thus perform these checks outside of the lock with a >> data_race() annotated variable read and fail quickly without taking the >> lock. >> >> Checks for sheaf availability that racily succeed have to be obviously >> repeated under the lock for correctness, but we can skip repeating >> checks if there are too many sheaves on the given list as the limits >> don't need to be strict. >> >> Signed-off-by: Vlastimil Babka > > Looks good to me, > Reviewed-by: Harry Yoo > > in kmem_cache_return_sheaf: >> if (!pcs->spare) { >> pcs->spare = sheaf; >> sheaf = NULL; >> } else if (pcs->barn->nr_full >= MAX_FULL_SHEAVES) { >> /* racy check */ >> barn = pcs->barn; >> keep = true; >> } > > By the way this code also needs data_race()? Right, will add, thanks.