tree 60e61ee495c95c0bdc78b35ad15178c8f7bef368
parent 78f548f49eae95ab098a2727bc44bee2e3d81b4f
author Willy Tarreau <w@1wt.eu> 1544005167 +0100
committer Willy Tarreau <w@1wt.eu> 1544005421 +0100
encoding latin1

MEDIUM: mux-h1: avoid a double copy on the Tx path whenever possible

In order to properly deal with unaligned contents, the output data are
currently copied into a temporary buffer, to be copied into the mux's
output buffer at the end. The new buffer API allows several buffers to
share the same data area, so we're using this here to make the temporary
buffer point to the same area as the output buffer when that one is
empty. This is enough to avoid the copy at the end, only pointers and
lengths have to be adjusted. In addition the output buffer's head is
advanced by the HTX header size so that the remaining copy is aligned.

By doing this we improve the large object performance by an extra 10%,
which is 64% above the 1.9-dev9 state. It's worth noting that there are
no more calls to __memcpy_sse2_unaligned() now.

Since this code deals with various block types, it appears difficult to
adjust it to be smart enough to even avoid the first copy. However a
distinct approach could consist in trying to detect a single blocked
HTX and jump to dedicated code in this case.