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repo: Only use mmap() for metadata > 16k 

See http://stackoverflow.com/questions/258091/when-should-i-use-mmap-for-file-access
and
https://lwn.net/Articles/591978/

I didn't really notice much performance difference in some small
tests, but I happened to be stracing and realized we were `mmap()`ing
even for 50 bytes which is not very useful, so let's not do it.

Closes: #489
Approved by: alexlarsson
This commit is contained in:
Colin Walters 2016-09-01 16:09:30 -04:00 committed by Atomic Bot
parent 8dbb104cdc
commit e127070550
1 changed files with 34 additions and 22 deletions
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56
src/libostree/ostree-repo.c
View File

@ -2544,6 +2544,7 @@ load_metadata_internal (OstreeRepo *self,
{
gboolean ret = FALSE;
char loose_path_buf[_OSTREE_LOOSE_PATH_MAX];
struct stat stbuf;
glnx_fd_close int fd = -1;
g_autoptr(GInputStream) ret_stream = NULL;
g_autoptr(GVariant) ret_variant = NULL;
@ -2565,23 +2566,39 @@ load_metadata_internal (OstreeRepo *self,
if (fd != -1)
{
if (fstat (fd, &stbuf) < 0)
{
glnx_set_error_from_errno (error);
goto out;
}
if (out_variant)
{
GMappedFile *mfile;
/* http://stackoverflow.com/questions/258091/when-should-i-use-mmap-for-file-access */
if (stbuf.st_size > 16*1024)
{
GMappedFile *mfile;
mfile = g_mapped_file_new_from_fd (fd, FALSE, error);
if (!mfile)
goto out;
ret_variant = g_variant_new_from_data (ostree_metadata_variant_type (objtype),
g_mapped_file_get_contents (mfile),
g_mapped_file_get_length (mfile),
TRUE,
(GDestroyNotify) g_mapped_file_unref,
mfile);
g_variant_ref_sink (ret_variant);
if (out_size)
*out_size = g_variant_get_size (ret_variant);
mfile = g_mapped_file_new_from_fd (fd, FALSE, error);
if (!mfile)
goto out;
ret_variant = g_variant_new_from_data (ostree_metadata_variant_type (objtype),
g_mapped_file_get_contents (mfile),
g_mapped_file_get_length (mfile),
TRUE,
(GDestroyNotify) g_mapped_file_unref,
mfile);
g_variant_ref_sink (ret_variant);
}
else
{
GBytes *data = glnx_fd_readall_bytes (fd, cancellable, error);
if (!data)
goto out;
ret_variant = g_variant_new_from_bytes (ostree_metadata_variant_type (objtype),
data, TRUE);
g_variant_ref_sink (ret_variant);
}
}
else if (out_stream)
{
@ -2589,15 +2606,10 @@ load_metadata_internal (OstreeRepo *self,
if (!ret_stream)
goto out;
fd = -1; /* Transfer ownership */
if (out_size)
{
struct stat stbuf;
if (!glnx_stream_fstat ((GFileDescriptorBased*)ret_stream, &stbuf, error))
goto out;
*out_size = stbuf.st_size;
}
}
if (out_size)
*out_size = stbuf.st_size;
}
else if (self->parent_repo)
{