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[70.77.216.213]) by smtp.gmail.com with ESMTPSA id k4sm4101238pgk.1.2019.03.29.14.52.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Mar 2019 14:52:35 -0700 (PDT) From: Andreas Dilger Message-Id: Content-Type: multipart/signed; boundary="Apple-Mail=_BC80F2B2-9665-432E-B261-89B3C9ECD293"; protocol="application/pgp-signature"; micalg=pgp-sha256 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: [PATCH] jbd2: do not start commit when t_updates does not back to zero Date: Fri, 29 Mar 2019 15:52:27 -0600 In-Reply-To: <20190329212523.GC8757@quack2.suse.cz> Cc: Liu Song , tytso@mit.edu, jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, liu.song11@zte.com.cn To: Jan Kara References: <20190324033835.55858-1-fishland@aliyun.com> <20190329212523.GC8757@quack2.suse.cz> X-Mailer: Apple Mail (2.3273) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Apple-Mail=_BC80F2B2-9665-432E-B261-89B3C9ECD293 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii On Mar 29, 2019, at 3:25 PM, Jan Kara wrote: >=20 > On Sun 24-03-19 11:38:35, Liu Song wrote: >> When t_updates back to zero, it guaranteed wake up process which >> waiting on j_wait_updates. If we triggered a commit start without >> considered t_updates, the commit thread wakes up and find t_updates >> is not zero, it have to wait on it once again. So, add checking code >> to avoid this happen. >>=20 >> Signed-off-by: Liu Song >=20 > Do I understand correctly that this is a performance improvement? If = yes, > did you measure any benefit of the patch? Because I have some doubts = that > t_updates =3D=3D 0 case is very common. In the past there have been times when periodic journal commits keep a = disk from spinning down, but I don't know if that is the case here... Cheers, Andreas >> --- >> fs/jbd2/transaction.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >>=20 >> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c >> index 79a028a7a579..e0499fd73b1e 100644 >> --- a/fs/jbd2/transaction.c >> +++ b/fs/jbd2/transaction.c >> @@ -144,12 +144,13 @@ static void wait_transaction_locked(journal_t = *journal) >> __releases(journal->j_state_lock) >> { >> DEFINE_WAIT(wait); >> - int need_to_start; >> + int need_to_start =3D 0; >> tid_t tid =3D journal->j_running_transaction->t_tid; >>=20 >> prepare_to_wait(&journal->j_wait_transaction_locked, &wait, >> TASK_UNINTERRUPTIBLE); >> - need_to_start =3D !tid_geq(journal->j_commit_request, tid); >> + if (!atomic_read(&journal->j_running_transaction->t_updates)) >> + need_to_start =3D !tid_geq(journal->j_commit_request, = tid); >> read_unlock(&journal->j_state_lock); >> if (need_to_start) >> jbd2_log_start_commit(journal, tid); >> -- >> 2.19.1 >>=20 >>=20 > -- > Jan Kara > SUSE Labs, CR Cheers, Andreas --Apple-Mail=_BC80F2B2-9665-432E-B261-89B3C9ECD293 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIzBAEBCAAdFiEEDb73u6ZejP5ZMprvcqXauRfMH+AFAlyek54ACgkQcqXauRfM H+CPkQ//fnziWA69QSL0P2ssmjqFD356Va9kU+SzNPmMLRts92WFN/P6gGpQZ2VI hC2At76cdOeEWkLCFr6RaUIHCl8BHOJwmP+5BAtkcXwpkk/P1NgJ3Xjiv0KGMFMb qc9VYLv0zJ3O7IMl/abgEOj7h1/FBCZBxOXgP4SmKWpJOuulUcKtxckqsjizeSBK yCsV6NmTPSXWS63FMDF0lJWDvyXXMQzTVQiuJUHMODR9Jcj6KTiD6EYHHHhffjLA mjVcNc/YXK/rVzkEuNQPpqM9PtPGa95fyKDptt1QdiVHL9RJbGGqikIRJmFEAjxm BjQ3p42uRJ+ZW7yfPtRDlVRFojfXnFr8Hff5Tppsr84J5tRwJu3VDGGbdm2cwpOF d0XiR2J85PUNglVHYVtd9ELRLGUkue/S7vuofcbKvfXQCMhPTlDQlftpkagpdaSW NGfbwJNIKJH23y+rzWgWP7DmijhkhObGO4dpqnwrEWr+3tMuepqlNJQWvR6Gi6GI nULcTXwGg9NcsNebHpiD4v1V6JX704nwODwgdMOZ2ENgkavOtGFPgX+2NTmtLMnc 9JAfWfrcl/NmeD4Ql46tqouxcH6Pl0HocSVGLPLLjMJ5zZ0pLVXAEL0rxROwbxra LRa1aa7P9RVD4fwVvltivJ5q7L9I3KLnfblJI8I5a7IvjmBgnBA= =qK2c -----END PGP SIGNATURE----- --Apple-Mail=_BC80F2B2-9665-432E-B261-89B3C9ECD293--