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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201103211101.4221-1-dsterba@suse.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="LTfABizZBSY5EFVaZ0zJbwnIwB7Rut9EU" X-Provags-ID: V03:K1:JKXawh9Rd7tixaUUplIuBvxA8CB+7s4qFQ5APUpj2OPB6hXfycs XHY4XiS8BilD922l2B9PbnaYQ0F6YHAn/N99bpb9pjIlRToVrUuvCVQLTH1QWwcb3KqubU+ LpdH6t+TShdVw7Y32RwlzMT5ZPvpKZCVwxBWS0p/XzoJVu3U32EseeJEm6Vi8Ra2c+gQ3l+ 41NN/YjsmM0Oh1X1v3mTA== X-UI-Out-Filterresults: notjunk:1;V03:K0:9U0nUR7bovA=:b7SM0Bbasf73UXu8O0JQAa RMFDidlgVYpNOp8MdUg2SUkF6Tcy0Uuh7rPJr5U6OqgbexVCIEhZd36xylXPTtgWFuqVNwyQI Pt/iJBe4HYQvnnme4lWFyaj9M+b+ucRq8Bq/9Rjh0Lg2ojfHi8W10Trb0yb8plhNHYoxjk3uo t1BQkShexIbPfg8L1/tM42cdzrxBHH1QTJG/SyL69hpmeq/EihcYxP+5GYlztzZtSvThKUQ3U ViX9bw4oQwN6Ge7EqIj98I9DRStYflNC1/WuPfR9vCLKRTgx/hw4ydxjvw3w0Eat401sdsRhh McVvDRfayV78VzAqLzZXe+FaweAJ476tUEpa1HNDMJP9wG7vK96/LCv0sPxM3aZiNmkP592sF 7heEUpJR+dF4OtzKqXD+/wSe0GSkB+qbWcfcu/HXnyGGmsFs6O+qyhGyCzQLU73A2lgveYfYp ihNQ0H5gZi6h9N9dyiPLqlxPlwbTvV84Nm8XqkP+WinZSgifTG76v7BZsx2yzPB+U714FHjCV 2/ignHy/HkqvW3KIGVqKHrt5OoeQgFmgyQDVIKhe83ELbj4wH8vTcI6ZcVGijt426jQdDzX1I IhnYmSd1qpmtGCahXAaAvHFZ++0cEbveo+02fj2X97hie+mEJ/1yDOkIYPZRUEyuzRNzTRStS QM/jACXOKVxy+JyamMOZOPPAO1R6UyZXne6ifmac0w82219hq9J5pHGmMdXTNVIoQGZhE7OUj V7VyikYfxeUPi6Sj/9hMbg8DWyC3L2JjC+ox7mA1VZPOZ5OCxHSdGsP2lv3rjsZOhk2KMQQ8e tLE8Hdg21iwmsffmMc4ar4dwFOZ4kWd6+xM4ci9Z6oirQH/BGCb8umOOvEQX9enuYV1CyXpv6 ZcmJOQPGw2TdD5sm+mBQ== Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --LTfABizZBSY5EFVaZ0zJbwnIwB7Rut9EU Content-Type: multipart/mixed; boundary="tkqdsBJ5mnzHCIRtjnG0odRA6ZzB3PFyN" --tkqdsBJ5mnzHCIRtjnG0odRA6ZzB3PFyN Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2020/11/4 =E4=B8=8A=E5=8D=885:11, David Sterba wrote: > After the rwsem replaced the tree lock implementation, the extent buffe= r > got smaller but leaving some holes behind. By changing log_index type > and reordering, we can squeeze the size further to 240 bytes, measured = on > release config on x86_64. Log_index spans only 3 values and needs to be= > signed. >=20 > Before: >=20 > struct extent_buffer { > u64 start; /* 0 8= */ > long unsigned int len; /* 8 8= */ > long unsigned int bflags; /* 16 8= */ > struct btrfs_fs_info * fs_info; /* 24 8= */ > spinlock_t refs_lock; /* 32 4= */ > atomic_t refs; /* 36 4= */ > atomic_t io_pages; /* 40 4= */ > int read_mirror; /* 44 4= */ > struct callback_head callback_head __attribute__((__align= ed__(8))); /* 48 16 */ > /* --- cacheline 1 boundary (64 bytes) --- */ > pid_t lock_owner; /* 64 4= */ > bool lock_recursed; /* 68 1= */ >=20 > /* XXX 3 bytes hole, try to pack */ >=20 > struct rw_semaphore lock; /* 72 40= */ An off-topic question, for things like aotmic_t/spinlock_t and rw_semaphore, wouldn't various DEBUG options change their size? Do we need to consider such case, by moving them to the end of the structure, or we only consider production build for pa_hole? Thanks, Qu > short int log_index; /* 112 2= */ >=20 > /* XXX 6 bytes hole, try to pack */ >=20 > struct page * pages[16]; /* 120 128= */ >=20 > /* size: 248, cachelines: 4, members: 14 */ > /* sum members: 239, holes: 2, sum holes: 9 */ > /* forced alignments: 1 */ > /* last cacheline: 56 bytes */ > } __attribute__((__aligned__(8))); >=20 > After: >=20 > struct extent_buffer { > u64 start; /* 0 8= */ > long unsigned int len; /* 8 8= */ > long unsigned int bflags; /* 16 8= */ > struct btrfs_fs_info * fs_info; /* 24 8= */ > spinlock_t refs_lock; /* 32 4= */ > atomic_t refs; /* 36 4= */ > atomic_t io_pages; /* 40 4= */ > int read_mirror; /* 44 4= */ > struct callback_head callback_head __attribute__((__align= ed__(8))); /* 48 16 */ > /* --- cacheline 1 boundary (64 bytes) --- */ > pid_t lock_owner; /* 64 4= */ > bool lock_recursed; /* 68 1= */ > s8 log_index; /* 69 1= */ >=20 > /* XXX 2 bytes hole, try to pack */ >=20 > struct rw_semaphore lock; /* 72 40= */ > struct page * pages[16]; /* 112 128= */ >=20 > /* size: 240, cachelines: 4, members: 14 */ > /* sum members: 238, holes: 1, sum holes: 2 */ > /* forced alignments: 1 */ > /* last cacheline: 48 bytes */ > } __attribute__((__aligned__(8))); >=20 > Signed-off-by: David Sterba > --- > fs/btrfs/extent_io.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) >=20 > diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h > index 5403354de0e1..3c2bf21c54eb 100644 > --- a/fs/btrfs/extent_io.h > +++ b/fs/btrfs/extent_io.h > @@ -88,10 +88,10 @@ struct extent_buffer { > struct rcu_head rcu_head; > pid_t lock_owner; > bool lock_recursed; > - struct rw_semaphore lock; > - > /* >=3D 0 if eb belongs to a log tree, -1 otherwise */ > - short log_index; > + s8 log_index; > + > + struct rw_semaphore lock; > =20 > struct page *pages[INLINE_EXTENT_BUFFER_PAGES]; > #ifdef CONFIG_BTRFS_DEBUG >=20 --tkqdsBJ5mnzHCIRtjnG0odRA6ZzB3PFyN-- --LTfABizZBSY5EFVaZ0zJbwnIwB7Rut9EU Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAl+h62EACgkQwj2R86El /qjc3Qf/RQFRPMAVsB0J22Jy21IWm7P7zC3VlOz1mHg/8l+GTGQEHa1qF/r/Vtz0 DNeVueiODKPXtgT8/D/l0VBbyyPOpi894NjwrNHMhmEikyVMYSyUNoDD7qoXWfoa ee3yPqPydoNICaVMjsPfzRK21v2Cf9a1ZNv/XcsV7K0RIVcF6eK7R2DaOe4J/imI 8vFK2cwO0E/wljMDfSYCXyVJ5FwvZ+KLxCK4mM0sdZwFGxJjnO2+lDI2rfvnMo7i SjYDzAFAUI3pmtvIUzrk7qXt4ctoT76ke9FTbSRp3G42rhnMmPtE+wk7DG+UuDQx 35ylwrj8ZVHO/rTH5DFu77CM6onMGA== =Jis/ -----END PGP SIGNATURE----- --LTfABizZBSY5EFVaZ0zJbwnIwB7Rut9EU--