path: root/mboxd_windows.c
diff options
authorAndrew Jeffery <>2018-03-23 11:40:35 +1030
committerAndrew Jeffery <>2018-04-04 07:56:23 +0000
commit0d087f17f868587ca01259632ba0bd584b66aae4 (patch)
treec71ac35940f16ed5d2d52d0abe14abcb19ba3035 /mboxd_windows.c
parent912c9bdf938893e41c675f6cd97b7b00bcc83940 (diff)
mboxd_windows: Reset evicted windows
After copying a portion of the backing store to a window, create_map_window() "resizes" the window to the aligned-up size reported by copy_flash(). This allows use of the window size as the content size elsewhere in the codebase. However, if we needed to evict a window to satisfy a request, the window properties were not reset. This lead to inefficient use of the reserved memory by limiting the effective window size to the minimum size of all requests that were previously allocated the window in question. Inefficient use of reserved memory isn't the only side effect; the host takes an eye-watering hit to throughput that gets exponentionally worse over time: From the petitboot shell without the patch applied: / # time cat /dev/mtd0 > /dev/null real 0m 49.77s user 0m 0.00s sys 0m 49.76s / # time cat /dev/mtd0 > /dev/null real 1m 33.57s user 0m 0.00s sys 1m 33.55s / # time cat /dev/mtd0 > /dev/null real 4m 45.37s user 0m 0.00s sys 4m 45.35s / # time cat /dev/mtd0 > /dev/null real 9m 17.77s user 0m 0.00s sys 9m 17.76s / # And with the patch applied: / # time cat /dev/mtd0 > /dev/null real 0m 43.00s user 0m 0.00s sys 0m 42.99s / # time cat /dev/mtd0 > /dev/null real 0m 42.40s user 0m 0.00s sys 0m 42.39s / # time cat /dev/mtd0 > /dev/null real 0m 42.41s user 0m 0.00s sys 0m 42.39s / # Reset the properties to allow use of the entire reserved memory region allocated to the window, improving memory efficiency, throughput, and minimising throughput variance. Change-Id: I7be78ec5e0a9ee0caf31133b0861e333844b8975 Signed-off-by: Andrew Jeffery <>
Diffstat (limited to 'mboxd_windows.c')
1 files changed, 1 insertions, 0 deletions
diff --git a/mboxd_windows.c b/mboxd_windows.c
index 9742180..275f38a 100644
--- a/mboxd_windows.c
+++ b/mboxd_windows.c
@@ -568,6 +568,7 @@ int create_map_window(struct mbox_context *context,
if (!cur) {
MSG_DBG("No uninitialised window, evicting one\n");
cur = find_oldest_window(context);
+ reset_window(context, cur);
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