https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7e332208a0987fd91bf1afc8fa7a5647b53a5670
commit 7e332208a0987fd91bf1afc8fa7a5647b53a5670 Author: Corinna Vinschen <[email protected]> AuthorDate: Wed Jan 18 19:59:48 2023 +0100 Commit: Corinna Vinschen <[email protected]> CommitDate: Wed Jan 18 20:13:36 2023 +0100 Cygwin: open_shared: always bump next_address The new loop in open_shared has a subtil performance problem. Next_address is bumped only if mapping at this address failed. Every subsequent call to open_shared has a high probability having to call MapViewOfFileEx twice, because next_address is still set to the address of the last successful mapping. Avoid this by bumping next_address every time. While at it, fix a comment. Fixes: dc0fe7742b8c ("Cygwin: open_shared: try harder allocating a shared region") Signed-off-by: Corinna Vinschen <[email protected]> Diff: --- winsup/cygwin/mm/shared.cc | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/winsup/cygwin/mm/shared.cc b/winsup/cygwin/mm/shared.cc index eb798c2ddb5f..e68b506a9fff 100644 --- a/winsup/cygwin/mm/shared.cc +++ b/winsup/cygwin/mm/shared.cc @@ -159,25 +159,21 @@ open_shared (const WCHAR *name, int n, HANDLE& shared_h, DWORD size, /* Locate shared regions in the area between SHARED_REGIONS_ADDRESS_LOW and SHARED_REGIONS_ADDRESS_HIGH, retrying until we have a slot. - Don't use MapViewOfFile3 (loader deadlock during fork. */ + Don't use MapViewOfFile3 (STATUS_DLL_INIT_FAILED during fork). */ bool loop = false; - addr = (void *) next_address; do { + addr = (void *) next_address; shared = MapViewOfFileEx (shared_h, FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, 0, addr); - if (!shared) + next_address += wincap.allocation_granularity (); + if (next_address >= SHARED_REGIONS_ADDRESS_HIGH) { - next_address += wincap.allocation_granularity (); - if (next_address >= SHARED_REGIONS_ADDRESS_HIGH) - { - if (loop) - break; - next_address = SHARED_REGIONS_ADDRESS_LOW; - loop = true; - } - addr = (void *) next_address; + if (!shared && loop) + break; + next_address = SHARED_REGIONS_ADDRESS_LOW; + loop = true; } } while (!shared);
