Mercurial > hgrepos > Python > apps > py-cutils

changeset 60:21d2589c96b9

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Use madvise if available to sequentially read a file
author Franz Glasner <fzglas.hg@dom66.de>
date Tue, 08 Feb 2022 21:45:14 +0100
parents b96d3585e8ce
children c9f9401abc0c
files shasum.py
diffstat 1 files changed, 6 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/shasum.py	Tue Feb 08 21:27:13 2022 +0100
+++ b/shasum.py	Tue Feb 08 21:45:14 2022 +0100
@@ -481,6 +481,10 @@
             # NOTE: On Windows mmapped files with length 0 are not supported.
             #       So ensure to not call mmap.mmap() if the file size is 0.
             #
+            try:
+                madvise = mmap.mmap.madvise
+            except AttributeError:
+                madvise = None
             if filesize < MAP_CHUNK_SIZE:
                 mapsize = filesize
             else:
@@ -492,6 +496,8 @@
                               mapsize,
                               access=mmap.ACCESS_READ,
                               offset=mapoffset)
+                if madvise:
+                    madvise(m, mmap.MADV_SEQUENTIAL)
                 try:
                     h.update(m)
                 finally: