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Wysocki" Cc: linux-kernel@vger.kernel.org, pbonzini@redhat.com, rkrcmar@redhat.com, rafael.j.wysocki@intel.com, joao.m.martins@oracle.com, mtosatti@redhat.com, kvm@vger.kernel.org, linux-pm@vger.kernel.org References: <1573041302-4904-1-git-send-email-zhenzhong.duan@oracle.com> <1573041302-4904-4-git-send-email-zhenzhong.duan@oracle.com> <6161954.sKiXg2khOt@kreacher> From: Zhenzhong Duan Organization: Oracle Corporation Message-ID: <5ff7cb30-b6fb-d9df-ee8d-bf21b95c9cb1@oracle.com> Date: Sun, 17 Nov 2019 16:57:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <6161954.sKiXg2khOt@kreacher> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9443 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911170086 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9443 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911170086 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/11/15 18:45, Rafael J. Wysocki wrote: > On Wednesday, November 6, 2019 12:55:01 PM CET Zhenzhong Duan wrote: >> As user can adjust guest_halt_poll_grow_start and guest_halt_poll_ns >> which leads to cpu_halt_poll_us beyond the two boundaries. This patch >> ensures cpu_halt_poll_us in that scope. >> >> If guest_halt_poll_shrink is 0, shrink the cpu_halt_poll_us to >> guest_halt_poll_grow_start instead of 0. To disable poll we can set >> guest_halt_poll_ns to 0. >> >> If user wrongly set guest_halt_poll_grow_start > guest_halt_poll_ns > 0, >> guest_halt_poll_ns take precedency and poll time is a fixed value of >> guest_halt_poll_ns. >> >> Signed-off-by: Zhenzhong Duan >> --- >> drivers/cpuidle/governors/haltpoll.c | 28 +++++++++++++--------------- >> 1 file changed, 13 insertions(+), 15 deletions(-) >> >> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c >> index 660859d..4a39df4 100644 >> --- a/drivers/cpuidle/governors/haltpoll.c >> +++ b/drivers/cpuidle/governors/haltpoll.c >> @@ -97,32 +97,30 @@ static int haltpoll_select(struct cpuidle_driver *drv, >> >> static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us) >> { >> - unsigned int val; >> + unsigned int val = dev->poll_limit_ns; > Not necessary to initialize it here. Then an random val may bypass all the check and get assigned to dev->poll_limit_ns if guest_halt_poll_grow_start< block_ns< uninitialized val< guest_halt_poll_ns With my change, dev->poll_limit_ns will not be changed in that case, logic same as original code. > >> u64 block_ns = block_us*NSEC_PER_USEC; >> >> /* Grow cpu_halt_poll_us if >> - * cpu_halt_poll_us < block_ns < guest_halt_poll_us >> + * cpu_halt_poll_us < block_ns <= guest_halt_poll_us > You could update the comment to say "dev->poll_limit_ns" instead of > "cpu_halt_poll_us" while at it. Will do, also guest_halt_poll_us to guest_halt_poll_ns > >> */ >> - if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { >> + if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns && >> + guest_halt_poll_grow) > The "{" brace is still needed as per the coding style and I'm not sure why > to avoid guest_halt_poll_grow equal to zero here? Will add "{}" and remove guest_halt_poll_grow check. My inital thought was to prevent dev->poll_limit_ns get shrinked with guest_halt_poll_grow=0. > >> val = dev->poll_limit_ns * guest_halt_poll_grow; >> - >> - if (val < guest_halt_poll_grow_start) >> - val = guest_halt_poll_grow_start; >> - if (val > guest_halt_poll_ns) >> - val = guest_halt_poll_ns; >> - >> - dev->poll_limit_ns = val; >> - } else if (block_ns > guest_halt_poll_ns && >> - guest_halt_poll_allow_shrink) { >> + else if (block_ns > guest_halt_poll_ns && >> + guest_halt_poll_allow_shrink) { >> unsigned int shrink = guest_halt_poll_shrink; >> >> - val = dev->poll_limit_ns; >> if (shrink == 0) >> - val = 0; >> + val = guest_halt_poll_grow_start; > That's going to be corrected below, so the original code would be fine. val was assigned twice using 'val = 0' while it's once with my change, optimal a bit? > >> else >> val /= shrink; > Here you can do > > val = dev->poll_limit_ns / shrink; Any special reason？Looks no difference for me. > >> - dev->poll_limit_ns = val; >> } >> + if (val < guest_halt_poll_grow_start) >> + val = guest_halt_poll_grow_start; > Note that guest_halt_poll_grow_start is in us (as per the comment next to its > definition and the initial value). That is a bug in the original code too, > but anyway. Good catch! will fix the comment. The default 50000ns vs 50000us, looks author means ns. guest_halt_poll_ns defaults to 200000, also hints ns for guest_halt_poll_grow_start. Thanks Zhenzhong