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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id q190sm775656ljb.29.2020.06.18.11.48.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jun 2020 11:48:52 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 18 Jun 2020 20:48:50 +0200 To: Matthew Wilcox Cc: Uladzislau Rezki , "Paul E. McKenney" , LKML , linux-mm@kvack.org, Andrew Morton , "Theodore Y . Ts'o" , Joel Fernandes , RCU , Oleksiy Avramchenko Subject: Re: [PATCH v2 09/16] rcu/tree: Maintain separate array for vmalloc ptrs Message-ID: <20200618184850.GA15211@pc636> References: <20200525214800.93072-1-urezki@gmail.com> <20200525214800.93072-10-urezki@gmail.com> <20200617234609.GA10087@paulmck-ThinkPad-P72> <20200618172504.GA14613@pc636> <20200618173206.GS2723@paulmck-ThinkPad-P72> <20200618175623.GA14865@pc636> <20200618181541.GS8681@bombadil.infradead.org> <20200618182333.GA15082@pc636> <20200618183751.GT8681@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200618183751.GT8681@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 31A5A20001B6E2CB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 18, 2020 at 11:37:51AM -0700, Matthew Wilcox wrote: > On Thu, Jun 18, 2020 at 08:23:33PM +0200, Uladzislau Rezki wrote: > > > +void vfree_bulk(size_t count, void **addrs) > > > +{ > > > + unsigned int i; > > > + > > > + BUG_ON(in_nmi()); > > > + might_sleep_if(!in_interrupt()); > > > + > > > + for (i = 0; i < count; i++) { > > > + void *addr = addrs[i]; > > > + kmemleak_free(addr); > > > + if (addr) > > > + __vfree(addr); > > > + } > > > +} > > > +EXPORT_SYMBOL(vfree_bulk); > > > + > > > > > Can we just do addrs[i] all over the loop? > > > > Also, we can just call vfree() instead that has all checking we > > need: NMI, kmemleak, might_sleep. > > Of course we _can_. But would we want to? This way, we only do these > checks once instead of once per pointer, which is rather the point > of batching. > Ahh, right. I briefly looked at it and missed that point. Right you are we do not want the vfree() here! > > I might actually go further and hoist the in_interrupt() check into > this function ... > Why do you need it? Just to inline below code: if (unlikely(in_interrupt())) __vfree_deferred(addr); else __vunmap(addr, 1); and bypass the __vfree() call(that is not marked as inline one)? I mean to inline above into vfree_bulk(). > > I suspect the RCU code always runs in_interrupt() > and so we always call vfree_deferred(). > No. We release the memory from workqueue context. -- Vlad Rezki