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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id 6sm7881530ejx.82.2021.09.21.10.50.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Sep 2021 10:50:59 -0700 (PDT) Subject: Re: [PATCH] KVM: do not shrink halt_poll_ns below grow_start To: Sergey Senozhatsky Cc: Suleiman Souhlal , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210902031100.252080-1-senozhatsky@chromium.org> From: Paolo Bonzini Message-ID: Date: Tue, 21 Sep 2021 19:50:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/09/21 03:42, Sergey Senozhatsky wrote: > On (21/09/02 12:11), Sergey Senozhatsky wrote: >> grow_halt_poll_ns() ignores values between 0 and >> halt_poll_ns_grow_start (10000 by default). However, >> when we shrink halt_poll_ns we may fall way below >> halt_poll_ns_grow_start and endup with halt_poll_ns >> values that don't make a lot of sense: like 1 or 9, >> or 19. >> >> VCPU1 trace (halt_poll_ns_shrink equals 2): >> >> VCPU1 grow 10000 >> VCPU1 shrink 5000 >> VCPU1 shrink 2500 >> VCPU1 shrink 1250 >> VCPU1 shrink 625 >> VCPU1 shrink 312 >> VCPU1 shrink 156 >> VCPU1 shrink 78 >> VCPU1 shrink 39 >> VCPU1 shrink 19 >> VCPU1 shrink 9 >> VCPU1 shrink 4 >> >> Mirror what grow_halt_poll_ns() does and set halt_poll_ns >> to 0 as soon as new shrink-ed halt_poll_ns value falls >> below halt_poll_ns_grow_start. > > Gentle ping. > > -ss > Queued, thanks. Paolo