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[34.86.60.15]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-47209a1b133sm14864501cf.70.2025.02.19.18.46.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Feb 2025 18:46:01 -0800 (PST) Date: Wed, 19 Feb 2025 21:46:01 -0500 From: Willem de Bruijn To: Jason Xing , Willem de Bruijn Cc: Martin KaFai Lau , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, willemb@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, ykolal@fb.com, bpf@vger.kernel.org, netdev@vger.kernel.org Message-ID: <67b697697bdf8_20efb0294b4@willemb.c.googlers.com.notmuch> In-Reply-To: References: <20250218050125.73676-1-kerneljasonxing@gmail.com> <20250218050125.73676-2-kerneljasonxing@gmail.com> <67b497b974fc3_10d6a32948b@willemb.c.googlers.com.notmuch> <03553725-648d-467f-9076-0d5c22b3cfb3@linux.dev> <67b542b9c4e3d_1692112944@willemb.c.googlers.com.notmuch> <67b5f4f5990b0_1b78d829412@willemb.c.googlers.com.notmuch> Subject: Re: [PATCH bpf-next v12 01/12] bpf: add networking timestamping support to bpf_get/setsockopt() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit > > Can you find a hole further down to place this in, or at least a spot > > that does not result in 7b of wasted space (in the hotpath cacheline > > groups of all places). > > There is one place where I can simply insert the flag. > > The diff patch on top of this series is: > diff --git a/include/net/sock.h b/include/net/sock.h > index e85d6fb3a2ba..9fa27693fb02 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -446,8 +446,6 @@ struct sock { > u32 sk_reserved_mem; > int sk_forward_alloc; > u32 sk_tsflags; > -#define SK_BPF_CB_FLAG_TEST(SK, FLAG) ((SK)->sk_bpf_cb_flags & (FLAG)) > - u8 sk_bpf_cb_flags; > __cacheline_group_end(sock_write_rxtx); > > __cacheline_group_begin(sock_write_tx); > @@ -528,6 +526,8 @@ struct sock { > u8 sk_txtime_deadline_mode : 1, > sk_txtime_report_errors : 1, > sk_txtime_unused : 6; > +#define SK_BPF_CB_FLAG_TEST(SK, FLAG) ((SK)->sk_bpf_cb_flags & (FLAG)) > + u8 sk_bpf_cb_flags; > > void *sk_user_data; > #ifdef CONFIG_SECURITY > > > 1) before applying the whole series: > ... > /* --- cacheline 10 boundary (640 bytes) --- */ > ktime_t sk_stamp; /* 0x280 0x8 */ > int sk_disconnects; /* 0x288 0x4 */ > u8 sk_txrehash; /* 0x28c 0x1 */ > u8 sk_clockid; /* 0x28d 0x1 */ > u8 sk_txtime_deadline_mode:1; /* 0x28e: 0 0x1 */ > u8 sk_txtime_report_errors:1; /* > 0x28e:0x1 0x1 */ > u8 sk_txtime_unused:6; /* 0x28e:0x2 0x1 */ > > /* XXX 1 byte hole, try to pack */ > > void * sk_user_data; /* 0x290 0x8 */ > void * sk_security; /* 0x298 0x8 */ > struct sock_cgroup_data sk_cgrp_data; /* 0x2a0 0x10 */ > ... > /* sum members: 773, holes: 1, sum holes: 1 */ > > > 2) after applying the series with the above diff patch: > ... > /* --- cacheline 10 boundary (640 bytes) --- */ > ktime_t sk_stamp; /* 0x280 0x8 */ > int sk_disconnects; /* 0x288 0x4 */ > u8 sk_txrehash; /* 0x28c 0x1 */ > u8 sk_clockid; /* 0x28d 0x1 */ > u8 sk_txtime_deadline_mode:1; /* 0x28e: 0 0x1 */ > u8 sk_txtime_report_errors:1; /* > 0x28e:0x1 0x1 */ > u8 sk_txtime_unused:6; /* 0x28e:0x2 0x1 */ > u8 sk_bpf_cb_flags; /* 0x28f 0x1 */ > void * sk_user_data; /* 0x290 > 0x8 */ > void * sk_security; /* 0x298 0x8 */ > struct sock_cgroup_data sk_cgrp_data; /* 0x2a0 0x10 */ > ... > /* sum members: 774 */ > > It turns out that the new sk_bpf_cb_flags fills the hole exactly. The > new field and some of its nearby fields are quite similar because they > are only/nearly written during the creation or setsockopt phase. > > I think now it's a good place to insert the new flag? Thanks. This seems fine to me.