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[82.29.237.198]) by smtp.gmail.com with ESMTPSA id f5sm2664602wrs.5.2021.07.27.12.01.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 12:01:18 -0700 (PDT) Date: Tue, 27 Jul 2021 20:01:15 +0100 From: "Dr. David Alan Gilbert" To: David Hildenbrand Subject: Re: [PATCH v2 3/6] util/oslib-posix: Don't create too many threads with small memory or little pages Message-ID: References: <20210722123635.60608-1-david@redhat.com> <20210722123635.60608-4-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210722123635.60608-4-david@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.717, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pankaj Gupta , Daniel P =?iso-8859-1?Q?=2E_Berrang=E9?= , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Igor Mammedov , Paolo Bonzini , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * David Hildenbrand (david@redhat.com) wrote: > Let's limit the number of threads to something sane, especially that > - We don't have more threads than the number of pages we have > - We don't have threads that initialize small (< 64 MiB) memory > > Signed-off-by: David Hildenbrand Reviewed-by: Dr. David Alan Gilbert > --- > util/oslib-posix.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/util/oslib-posix.c b/util/oslib-posix.c > index 2ae6c3aaab..a1d309d495 100644 > --- a/util/oslib-posix.c > +++ b/util/oslib-posix.c > @@ -40,6 +40,7 @@ > #include > #include "qemu/cutils.h" > #include "qemu/compiler.h" > +#include "qemu/units.h" > > #ifdef CONFIG_LINUX > #include > @@ -529,7 +530,8 @@ static void *do_madv_populate_write_pages(void *arg) > return NULL; > } > > -static inline int get_memset_num_threads(int smp_cpus) > +static inline int get_memset_num_threads(size_t hpagesize, size_t numpages, > + int smp_cpus) > { > long host_procs = sysconf(_SC_NPROCESSORS_ONLN); > int ret = 1; > @@ -537,6 +539,12 @@ static inline int get_memset_num_threads(int smp_cpus) > if (host_procs > 0) { > ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus); > } > + > + /* Especially with gigantic pages, don't create more threads than pages. */ > + ret = MIN(ret, numpages); > + /* Don't start threads to prealloc comparatively little memory. */ > + ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB))); > + > /* In case sysconf() fails, we fall back to single threaded */ > return ret; > } > @@ -546,7 +554,7 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages, > { > static gsize initialized = 0; > MemsetContext context = { > - .num_threads = get_memset_num_threads(smp_cpus), > + .num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus), > }; > size_t numpages_per_thread, leftover; > void *(*touch_fn)(void *); > -- > 2.31.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK