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authorLasse Collin <lasse.collin@tukaani.org>2020-01-26 14:13:42 +0200
committerLasse Collin <lasse.collin@tukaani.org>2020-02-05 22:00:28 +0200
commitec26f3ace5f9b260ca91508030f07465ae2f9f78 (patch)
tree36c2c61c775b6e449c05254901796a3efbd93ba2 /src/xz/file_io.c
parentxz: Refactor io_read() a bit. (diff)
downloadxz-ec26f3ace5f9b260ca91508030f07465ae2f9f78.tar.xz
xz: Fix semi-busy-waiting in xz --flush-timeout.
When input blocked, xz --flush-timeout=1 would wake up every millisecond and initiate flushing which would have nothing to flush and thus would just waste CPU time. The fix disables the timeout when no input has been seen since the previous flush.
Diffstat (limited to '')
-rw-r--r--src/xz/file_io.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index 1512cc12..04e58c51 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -749,6 +749,7 @@ io_open_src(const char *src_name)
.src_fd = -1,
.dest_fd = -1,
.src_eof = false,
+ .src_has_seen_input = false,
.dest_try_sparse = false,
.dest_pending_sparse = 0,
};
@@ -1133,10 +1134,15 @@ io_read(file_pair *pair, io_buf *buf, size_t size)
#ifndef TUKLIB_DOSLIKE
if (IS_EAGAIN_OR_EWOULDBLOCK(errno)) {
- const io_wait_ret ret = io_wait(pair,
- mytime_get_flush_timeout(),
- true);
- switch (ret) {
+ // Disable the flush-timeout if no input has
+ // been seen since the previous flush and thus
+ // there would be nothing to flush after the
+ // timeout expires (avoids busy waiting).
+ const int timeout = pair->src_has_seen_input
+ ? mytime_get_flush_timeout()
+ : -1;
+
+ switch (io_wait(pair, timeout, true)) {
case IO_WAIT_MORE:
continue;
@@ -1160,6 +1166,7 @@ io_read(file_pair *pair, io_buf *buf, size_t size)
}
pos += (size_t)(amount);
+ pair->src_has_seen_input = true;
}
return pos;