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Wed, 24 May 2023 05:44:01 -0400 X-MC-Unique: VA7xbkGEO1yp0XxMlHptJQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 938AF800159; Wed, 24 May 2023 09:44:00 +0000 (UTC) Received: from localhost (ovpn-12-35.pek2.redhat.com [10.72.12.35]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E60141121314; Wed, 24 May 2023 09:43:59 +0000 (UTC) Date: Wed, 24 May 2023 17:43:56 +0800 From: Baoquan He To: Thomas Gleixner Cc: linux-mm@kvack.org, Andrew Morton , Christoph Hellwig , Uladzislau Rezki , Lorenzo Stoakes , Peter Zijlstra Subject: Re: [patch 3/6] mm/vmalloc: Prevent flushing dirty space over and over Message-ID: References: <20230523135902.517032811@linutronix.de> <20230523140002.690874212@linutronix.de> MIME-Version: 1.0 In-Reply-To: <20230523140002.690874212@linutronix.de> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4E0E64000F X-Stat-Signature: tcn5kpz3tcurya7r7cpqdtc5oqsze9bx X-Rspam-User: X-HE-Tag: 1684921445-851322 X-HE-Meta: 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 OfENgjB5 aSHmXGWLrNWrzhgLPI9B0EmgSheYScLIMxQTBWjcLiKsN57JGNFa3XZwzJE8qG1otAT/FcKedVvSt5/YpNKJg6u/jNfnGAdan0JTpQWDi0weHE8hboqulGVD4HlrJl24V8dtn737ToS6Z7qDSPtbGe83p04MCaJgFcJVEC3IHc4yMVCSr5R04JyOpOroo3Wx2AvvAla8CmEjTVfu3rNXC9BFexxMhkGinbrf9 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 05/23/23 at 04:02pm, Thomas Gleixner wrote: > vmap blocks which have active mappings cannot be purged. Allocations which > have been freed are accounted for in vmap_block::dirty_min/max, so that > they can be detected in _vm_unmap_aliases() as potentially stale TLBs. > > If there are several invocations of _vm_unmap_aliases() then each of them > will flush the dirty range. That's pointless and just increases the > probability of full TLB flushes. > > Avoid that by resetting the flush range after accounting for it. That's > safe versus other invocations of _vm_unmap_aliases() because this is all > serialized with vmap_purge_lock. > > Signed-off-by: Thomas Gleixner > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2224,7 +2224,7 @@ static void vb_free(unsigned long addr, > > spin_lock(&vb->lock); > > - /* Expand dirty range */ > + /* Expand the not yet TLB flushed dirty range */ > vb->dirty_min = min(vb->dirty_min, offset); > vb->dirty_max = max(vb->dirty_max, offset + (1UL << order)); > > @@ -2262,7 +2262,7 @@ static void _vm_unmap_aliases(unsigned l > * space to be flushed. > */ > if (!purge_fragmented_block(vb, vbq, &purge_list) && > - vb->dirty && vb->dirty != VMAP_BBMAP_BITS) { > + vb->dirty_max && vb->dirty != VMAP_BBMAP_BITS) { > unsigned long va_start = vb->va->va_start; > unsigned long s, e; > > @@ -2272,6 +2272,10 @@ static void _vm_unmap_aliases(unsigned l > start = min(s, start); > end = max(e, end); > > + /* Prevent that this is flushed more than once */ > + vb->dirty_min = VMAP_BBMAP_BITS; > + vb->dirty_max = 0; > + This is really a great catch and improvement. Reviewed-by: Baoquan He > flush = 1; > } > spin_unlock(&vb->lock); >