From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH AUTOSEL 4.19 140/219] libceph: drop last_piece logic from write_partial_message_data() Date: Sun, 1 Dec 2019 09:34:36 -0500 Message-ID: <20191201143436.GS5861@sasha-vm> References: <20191122054911.1750-1-sashal@kernel.org> <20191122054911.1750-133-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ilya Dryomov Cc: LKML , stable@vger.kernel.org, Ceph Development , netdev List-Id: ceph-devel.vger.kernel.org On Fri, Nov 22, 2019 at 03:00:43PM +0100, Ilya Dryomov wrote: >On Fri, Nov 22, 2019 at 6:51 AM Sasha Levin wrote: >> >> From: Ilya Dryomov >> >> [ Upstream commit 1f6b821aef78e3d79e8d598ae59fc7e23fb6c563 ] >> >> last_piece is for the last piece in the current data item, not in the >> entire data payload of the message. This is harmful for messages with >> multiple data items. On top of that, we don't need to signal the end >> of a data payload either because it is always followed by a footer. >> >> We used to signal "more" unconditionally, until commit fe38a2b67bc6 >> ("libceph: start defining message data cursor"). Part of a large >> series, it introduced cursor->last_piece and also mistakenly inverted >> the hint by passing last_piece for "more". This was corrected with >> commit c2cfa1940097 ("libceph: Fix ceph_tcp_sendpage()'s more boolean >> usage"). >> >> As it is, last_piece is not helping at all: because Nagle algorithm is >> disabled, for a simple message with two 512-byte data items we end up >> emitting three packets: front + first data item, second data item and >> footer. Go back to the original pre-fe38a2b67bc6 behavior -- a single >> packet in most cases. >> >> Signed-off-by: Ilya Dryomov >> Signed-off-by: Sasha Levin >> --- >> net/ceph/messenger.c | 8 +++----- >> 1 file changed, 3 insertions(+), 5 deletions(-) >> >> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c >> index f7d7f32ac673c..6514816947fbe 100644 >> --- a/net/ceph/messenger.c >> +++ b/net/ceph/messenger.c >> @@ -1612,7 +1612,6 @@ static int write_partial_message_data(struct ceph_connection *con) >> struct page *page; >> size_t page_offset; >> size_t length; >> - bool last_piece; >> int ret; >> >> if (!cursor->resid) { >> @@ -1620,10 +1619,9 @@ static int write_partial_message_data(struct ceph_connection *con) >> continue; >> } >> >> - page = ceph_msg_data_next(cursor, &page_offset, &length, >> - &last_piece); >> - ret = ceph_tcp_sendpage(con->sock, page, page_offset, >> - length, !last_piece); >> + page = ceph_msg_data_next(cursor, &page_offset, &length, NULL); >> + ret = ceph_tcp_sendpage(con->sock, page, page_offset, length, >> + true); >> if (ret <= 0) { >> if (do_datacrc) >> msg->footer.data_crc = cpu_to_le32(crc); > >Hi Sasha, > >This commit was part of a larger series and shouldn't be backported on >its own. Please drop it. Now dropped, thanks! -- Thanks, Sasha