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[81.154.179.160]) by smtp.gmail.com with ESMTPSA id o12-20020adfe80c000000b002fe13ec49fasm8638777wrm.98.2023.05.27.11.19.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 27 May 2023 11:19:33 -0700 (PDT) Date: Sat, 27 May 2023 19:19:32 +0100 From: Lorenzo Stoakes To: Thomas Gleixner Cc: linux-mm@kvack.org, Andrew Morton , Christoph Hellwig , Uladzislau Rezki , Peter Zijlstra , Baoquan He Subject: Re: [V2 patch 3/6] mm/vmalloc: Prevent flushing dirty space over and over Message-ID: <590a1dc3-ce57-4d13-a9c8-82ac5832ab99@lucifer.local> References: <20230525122342.109672430@linutronix.de> <20230525124504.692056496@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230525124504.692056496@linutronix.de> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 13F0A12000E X-Stat-Signature: p37zf4rc4zgpesy7tq9hmitsmoin58tg X-HE-Tag: 1685211575-150491 X-HE-Meta: U2FsdGVkX1/61RR6C1lALyNnOghJ6Ume6vtzXC/GmSvW/NdH+lvoczuVc2fZ0B1s6fi+gkAs7d8XSO5shwfFraDao754d0wQyZ8yYJcrQOzdTaWGVw4VPKdHcWcA6RYYoORNjRhOp8FVl6YI24DnkTaYK2nQqL7c2RKdtGxasYJo4PFOEMgJHnPOk+HF+SiMj+x2Ndb6aANCXahf5DHZDSCcMeW6UVL4RH0y6t9zXbt0FGRxbKbcjiCpJYJplCSf3ARwSD7BYx1rDZzUglQMYx3z1PpD8mYcTriL8N6omjxn+eglzK7rcqP4wA+5jsLQuxGrLSJxpk2X8smj6mvjnw/ILLKmnGIt/uT4bcFpGM3jEm9Pl2vElMiQnzdt/XMWg/l5X+ueKgiIfVe9fhpO1Kb5g+aDMBuM/F+L9knKsIln20ywSD/cvANCeg+o9t1jsVhLOK7McP7fZhqnaE9/QsAcsRgR3BYNPKooJRFmEbC+asWwh2Dq/CbNjgLoQjCXrNhJ4zm1gixg8rV3qYE1K9AwfMOqIjPRAF/aeKwtvEUaH4uxTUxvB8w7KM+9aYDf7oLP/I/K3CEFrbO8yhn0JmR7euf38YwLc53SsDq4m+zXwrjckUYtkfA5AyPIxYlmfGAawMUQ7H+s1Vz8SG928Ky58ndjZCl/8IWrcDBDR+H5aaS809ZT0+s/PZ0qQgKbdkEsTVBD/kIY2tmbhMU6dCfv5YI4NJckc5cfSGFJqnQdL9pwUV/Ucj4AzyxQMUe5GEb748nzt67IP/cwERrhTLVXxnFq6piDNlnK39xUcbndE+QEFiOFuyaURm37RXu5nDlmJbhxwEjVD9NnmQ7amA6FIpKHCbBlkkwR5vlazYYF+QHj0q46nCHbUzvQAjsOy2LCIqerN0Cc0kvjp/kBeFzyckBqUiaiJXzvs2V9BQS7yfF10tL/t27igOa74I6Aj6sornYGXJSbxhRyaLH N/h/Sg9Z +G0fThbcyS+jTPrzcCItXSKlA4ZCC5HWLl6eY1dGyVHWY+aceoa+y/CU7F3Fpu5WZ7dB1LJNYa/dDMX3QQRrEo5t75WjK9qlU2Dh4OfL+EGrT2wbxAh10aKvUns5im6E7jA8P69aqSVSNFYZ/PfKqfZP8YNAHpTUGtpiMyJjo+93BGYNdIc9GwWLTDzSBrsSkjhzjB0LPI7zzSDEVb33c7zvgb87tZhIX8JQHeBKYhyICTgvQ0SHryGSq9B2FwYw/3aHcm9biVbfOYOo1Jpy5u3Y5jWmX8jOjI170iyoqvbXP30XBhnnwCcmUqgAn2sf9l/QmHGmMrqo34L0crTqMnElV1hHImkmBn+BDa1jW5cEjsAvmO8zFaB6GtINRcRzez4B2Up+6c06VwpmE7cEwrRsaMJwJ3JVwBIs4I70lms60a1GWanRAshWs9A== 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, May 25, 2023 at 02:57:05PM +0200, 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 > Reviewed-by: Baoquan He > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2226,7 +2226,7 @@ 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)); > > @@ -2264,7 +2264,7 @@ 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; > > @@ -2274,6 +2274,10 @@ static void _vm_unmap_aliases(unsigned l > start = min(s, start); > end = max(e, end); > > + /* Prevent that this is flushed again */ Sorry to be absurdly nitty, and I know there's other instances of this in vmalloc.c but it'd be nice to correct the grammar here -> 'prevent this from being flushed again'. However, far from urgent! > + vb->dirty_min = VMAP_BBMAP_BITS; > + vb->dirty_max = 0; > + > flush = 1; > } > spin_unlock(&vb->lock); > > This is a really good catch, feel free to add:- Reviewed-by: Lorenzo Stoakes