Better mmap() emulation #486
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It is not really helpful when a `git fetch` fails with the message: fatal: mmap failed: No error In the particular instance encountered by a colleague of yours truly, the Win32 error code was ERROR_COMMITMENT_LIMIT which means that the page file is not big enough. Let's make the message fatal: mmap failed: File too large instead, which is only marginally better, but which can be associated with the appropriate work-around: setting `core.packedGitWindowSize` to a relatively small value. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Often we are mmap()ing read-only. In those cases, it is wasteful to map in copy-on-write mode. Even worse: it can cause errors where we run out of space in the page file. So let's be extra careful to map files in read-only mode whenever possible. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
On Windows, we have to emulate the fstat() call to fill out information that takes extra effort to obtain, such as the file permissions/type. If all we want is the file size, we can use the much cheaper GetFileSizeEx() function (available since Windows XP). Suggested by Philip Kelley. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
| hmap = CreateFileMapping((HANDLE)_get_osfhandle(fd), NULL, | ||
| PAGE_WRITECOPY, 0, 0, NULL); | ||
| hmap = CreateFileMapping(osfhandle, NULL, | ||
| prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL); |
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Git for Windows » git #14 SUCCESS |
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... aaaand the test suite passed here, too. |
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@dscho Is this planned to be passed upstream? |
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@csware yes, of course ;-) Thanks for the reminder. |
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Kevin David provided access to his VM where a simple
git fetchwould produce this error output:The reason was that several bits of our
mmap()emulation left room for improvement. This Pull Request tries to close the gap.