aboutsummaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
authorShawn O. Pearce <spearce@spearce.org>2006-12-23 02:34:28 -0500
committerJunio C Hamano <junkio@cox.net>2006-12-29 11:36:45 -0800
commit60bb8b1453e2f93d13e7bb44e8e46c085d2dd752 (patch)
tree3203b1cd4a7479e0175a4c65462ea714ccdabd9b /Documentation
parent54044bf825d311751e30552248be1e0cac99a5a3 (diff)
downloadgit-60bb8b1453e2f93d13e7bb44e8e46c085d2dd752.tar.gz
git-60bb8b1453e2f93d13e7bb44e8e46c085d2dd752.tar.xz
Fully activate the sliding window pack access.
This finally turns on the sliding window behavior for packfile data access by mapping limited size windows and chaining them under the packed_git->windows list. We consider a given byte offset to be within the window only if there would be at least 20 bytes (one hash worth of data) accessible after the requested offset. This range selection relates to the contract that use_pack() makes with its callers, allowing them to access one hash or one object header without needing to call use_pack() for every byte of data obtained. In the worst case scenario we will map the same page of data twice into memory: once at the end of one window and once again at the start of the next window. This duplicate page mapping will happen only when an object header or a delta base reference is spanned over the end of a window and is always limited to just one page of duplication, as no sane operating system will ever have a page size smaller than a hash. I am assuming that the possible wasted page of virtual address space is going to perform faster than the alternatives, which would be to copy the object header or ref delta into a temporary buffer prior to parsing, or to check the window range on every byte during header parsing. We may decide to revisit this decision in the future since this is just a gut instinct decision and has not actually been proven out by experimental testing. Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/config.txt11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 28fe6942c..d71653dc6 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -118,6 +118,17 @@ core.legacyheaders::
database directly (where the "http://" and "rsync://" protocols
count as direct access).
+core.packedGitWindowSize::
+ Number of bytes of a pack file to map into memory in a
+ single mapping operation. Larger window sizes may allow
+ your system to process a smaller number of large pack files
+ more quickly. Smaller window sizes will negatively affect
+ performance due to increased calls to the opreating system's
+ memory manager, but may improve performance when accessing
+ a large number of large pack files. Default is 32 MiB,
+ which should be reasonable for all users/operating systems.
+ You probably do not need to adjust this value.
+
core.packedGitLimit::
Maximum number of bytes to map simultaneously into memory
from pack files. If Git needs to access more than this many