From 0fc51b569570e8bf5aecd5ee03a88eb668b7b385 Mon Sep 17 00:00:00 2001 From: Anita Zhang Date: Tue, 14 Sep 2021 16:33:10 -0700 Subject: [PATCH] fileio: start with 4k buffer for procfs There's a very gradual increase of anonymous memory in systemd-journald that blames to 2ac67221bb6270f0fbe7cbd0076653832cd49de2. systemd-journald makes many calls to read /proc/PID/cmdline and /proc/PID/status, both of which tend to be well under 4K. However the combination of allocating 4M read buffers, then using `realloc()` to shrink the buffer in `read_virtual_file()` appears to be creating fragmentation in the heap (when combined with the other allocations systemd-journald is doing). To help mitigate this, try reading /proc with a 4K buffer as `read_virtual_file()` did before 2ac67221bb6270f0fbe7cbd0076653832cd49de2. If it isn't big enough then try again with the larger buffers. --- src/basic/fileio.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/src/basic/fileio.c b/src/basic/fileio.c index 99a44fdea2..466c6321c7 100644 --- a/src/basic/fileio.c +++ b/src/basic/fileio.c @@ -431,6 +431,11 @@ int read_virtual_file(const char *filename, size_t max_size, char **ret_contents } n_retries--; + } else if (n_retries > 1) { + /* Files in /proc are generally smaller than the page size so let's start with a page size + * buffer from malloc and only use the max buffer on the final try. */ + size = MIN3(page_size() - 1, READ_VIRTUAL_BYTES_MAX, max_size); + n_retries = 1; } else { size = MIN(READ_VIRTUAL_BYTES_MAX, max_size); n_retries = 0; -- 2.31.1