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AJvYcCXmb9bIW7WDv4Nz6c4gPbXzudA+Bd3YxxZ40RwGTVCjZAVPUIKPQmV0aIRDHFv2l6jQo76zgUp6gw==@kvack.org X-Gm-Message-State: AOJu0YwGqVPUbEr2sM/UFdTNKzsl7wSVlGWFHCz5okykq8wOMWxwT8z3 QYgIVkFcPhFE+/YNa/V3gM7NU88ajYzsfRnb2aui0L79J1U43wcV5n7IM6/35HQOt28GrDdOGRV pK1fPR6+7fPSm9DWr7udPh4AucmK7NkDKIFfl X-Gm-Gg: ASbGncv8QJz2vZB6SjOLn1rx+2F7lI7L1F/6D65Am+6c5qJSc4WPCtiJIdkIvCrqtqZ ebVyr9mSAjUTflam1dPcc/ikXybYb1h/rg6bDRQWc+5x3QVNWxZgg3FmHbyfnQBIVD0TqOA+ybC KTT3zxB15uucwnkVDM4R5ir5tDl28= X-Google-Smtp-Source: AGHT+IH1CnRV5ltlIFYCD8r2z+kCU2AjYaHwGfhq6KhIQ8OE5guM8kGIum9PY0Ww3eZxM7IkjMsYobe9TP0B8I4TUWk= X-Received: by 2002:a05:622a:3d0:b0:447:e59b:54eb with SMTP id d75a77b69052e-471ce95ecd4mr1005091cf.26.1739487558542; Thu, 13 Feb 2025 14:59:18 -0800 (PST) MIME-Version: 1.0 References: <20250111042604.3230628-1-surenb@google.com> <20250111042604.3230628-13-surenb@google.com> <20250115105056.GY5388@noisy.programming.kicks-ass.net> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 13 Feb 2025 14:59:07 -0800 X-Gm-Features: AWEUYZmlg1kcVkmWqjyI70BvcBxyYcl4HVx6CnlwWZWv5s51alYwg7U7bzMVrGY Message-ID: Subject: Re: [PATCH v9 12/17] mm: move lesser used vma_area_struct members into the last cacheline To: Peter Zijlstra Cc: akpm@linux-foundation.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, richard.weiyang@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D396C180005 X-Stat-Signature: u6chwip139dcms1pg7fw8qc9kbb9rqt1 X-Rspam-User: X-HE-Tag: 1739487559-138355 X-HE-Meta: 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 hjDl9b63 f3qLHTHnBRDMdoa3hsU0DlF0pxl202ddNbH4kqnxRem31Lo3i0WzUS0I3VZ8SKIuiQi4S0IY2sdgchjaRsaEGoTU0una7MijgdEEny0ThNoASrrCh6x5tWTTqPA1kW8oK5W1n9VPbs6QauvGNqInJFGRmRfkAQHfpkXRjhaARSaxuch/GAeyB78/yuya8fK9A1uMsfUmoZNuW7rwzVko7okks+hYuz7mNzfxC1F1PqM9epPfWgtYrm1ayP6eW0YaGCEtmGdNsB/JcKdHzx4KIZPMjiihTfYPTjoOZ49b1Iiq+sJ9X18GK3yv4VjLSFqcJbc+kxHgRa9qdjD3FnectWO1gWPHku3oKE2BCdeAv28De01u3a2XKMa6Oo+QgvP+w8dEOLUDGT4nHhmA0QJ16WEojbeRNeZqslpZ+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jan 15, 2025 at 8:39=E2=80=AFAM Suren Baghdasaryan wrote: > > On Wed, Jan 15, 2025 at 2:51=E2=80=AFAM Peter Zijlstra wrote: > > > > On Fri, Jan 10, 2025 at 08:25:59PM -0800, Suren Baghdasaryan wrote: > > > Move several vma_area_struct members which are rarely or never used > > > during page fault handling into the last cacheline to better pack > > > vm_area_struct. As a result vm_area_struct will fit into 3 as opposed > > > to 4 cachelines. New typical vm_area_struct layout: > > > > > > struct vm_area_struct { > > > union { > > > struct { > > > long unsigned int vm_start; /* 0 8 *= / > > > long unsigned int vm_end; /* 8 8 *= / > > > }; /* 0 16 *= / > > > freeptr_t vm_freeptr; /* 0 8 *= / > > > }; /* 0 16 *= / > > > struct mm_struct * vm_mm; /* 16 8 *= / > > > pgprot_t vm_page_prot; /* 24 8 *= / > > > union { > > > const vm_flags_t vm_flags; /* 32 8 *= / > > > vm_flags_t __vm_flags; /* 32 8 *= / > > > }; /* 32 8 *= / > > > unsigned int vm_lock_seq; /* 40 4 *= / > > > > Does it not make sense to move this seq field near the refcnt? > > In an earlier version, when vm_lock was not a refcount yet, I tried > that and moving vm_lock_seq introduced regression in the pft test. We > have that early vm_lock_seq check in the beginning of vma_start_read() > and if it fails we bail out early without locking. I think that might > be the reason why keeping vm_lock_seq in the first cacheling is > beneficial. But I'll try moving it again now that we have vm_refcnt > instead of the lock and see if pft still shows any regression. I confirmed that moving vm_lock_seq next to vm_refcnt regresses pagefault performance: Hmean faults/cpu-1 508634.6876 ( 0.00%) 508548.5498 * -0.02%* Hmean faults/cpu-4 474767.2684 ( 0.00%) 475620.7653 * 0.18%* Hmean faults/cpu-7 451356.6844 ( 0.00%) 446738.2381 * -1.02%* Hmean faults/cpu-12 360114.9092 ( 0.00%) 337121.8189 * -6.38%* Hmean faults/cpu-21 227567.8237 ( 0.00%) 205277.2029 * -9.80%* Hmean faults/cpu-30 163383.6765 ( 0.00%) 152765.1451 * -6.50%* Hmean faults/cpu-48 118048.2568 ( 0.00%) 109959.2027 * -6.85%* Hmean faults/cpu-56 103189.6761 ( 0.00%) 92989.3749 * -9.89%* Hmean faults/sec-1 508228.4512 ( 0.00%) 508129.1963 * -0.02%* Hmean faults/sec-4 1854868.9033 ( 0.00%) 1862443.6146 * 0.41%* Hmean faults/sec-7 3088881.6158 ( 0.00%) 3050403.1664 * -1.25%* Hmean faults/sec-12 4222540.9948 ( 0.00%) 3951163.9557 * -6.43%* Hmean faults/sec-21 4555777.5386 ( 0.00%) 4130470.6021 * -9.34%* Hmean faults/sec-30 4336721.3467 ( 0.00%) 4150477.5095 * -4.29%* Hmean faults/sec-48 5163921.7465 ( 0.00%) 4857286.2166 * -5.94%* Hmean faults/sec-56 5413622.8890 ( 0.00%) 4936484.0021 * -8.81%* So, I kept it unchanged in v10 (https://lore.kernel.org/all/20250213224655.1680278-14-surenb@google.com/) > > > > > > /* XXX 4 bytes hole, try to pack */ > > > > > > struct list_head anon_vma_chain; /* 48 16 *= / > > > /* --- cacheline 1 boundary (64 bytes) --- */ > > > struct anon_vma * anon_vma; /* 64 8 *= / > > > const struct vm_operations_struct * vm_ops; /* 72 8 *= / > > > long unsigned int vm_pgoff; /* 80 8 *= / > > > struct file * vm_file; /* 88 8 *= / > > > void * vm_private_data; /* 96 8 *= / > > > atomic_long_t swap_readahead_info; /* 104 8 *= / > > > struct mempolicy * vm_policy; /* 112 8 *= / > > > struct vma_numab_state * numab_state; /* 120 8 *= / > > > /* --- cacheline 2 boundary (128 bytes) --- */ > > > refcount_t vm_refcnt (__aligned__(64)); /* 128 4 *= / > > > > > > /* XXX 4 bytes hole, try to pack */ > > > > > > struct { > > > struct rb_node rb (__aligned__(8)); /* 136 24 *= / > > > long unsigned int rb_subtree_last; /* 160 8 *= / > > > } __attribute__((__aligned__(8))) shared; /* 136 32 *= / > > > struct anon_vma_name * anon_name; /* 168 8 *= / > > > struct vm_userfaultfd_ctx vm_userfaultfd_ctx; /* 176 8 *= / > > > > > > /* size: 192, cachelines: 3, members: 18 */ > > > /* sum members: 176, holes: 2, sum holes: 8 */ > > > /* padding: 8 */ > > > /* forced alignments: 2, forced holes: 1, sum forced holes: 4 */ > > > } __attribute__((__aligned__(64))); > > > >