public inbox for cygwin-cvs@sourceware.org help / color / mirror / Atom feed
From: Corinna Vinschen <corinna@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin/cygwin-3_4-branch] Cygwin: open_shared: always bump next_address Date: Wed, 18 Jan 2023 19:35:09 +0000 (GMT) [thread overview] Message-ID: <20230118193509.DC3F43858D28@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=0aa1c038196d04d0dfc8dc0f0f30e247e0c1e1e3 commit 0aa1c038196d04d0dfc8dc0f0f30e247e0c1e1e3 Author: Corinna Vinschen <corinna@vinschen.de> AuthorDate: Wed Jan 18 19:59:48 2023 +0100 Commit: Corinna Vinschen <corinna@vinschen.de> CommitDate: Wed Jan 18 20:17:23 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. Conflict: Missing backport of 31302b267b86 ("Cygwin: drop fixed addresses for standard shared regions") Fixes: dc0fe7742b8c ("Cygwin: open_shared: try harder allocating a shared region") Signed-off-by: Corinna Vinschen <corinna@vinschen.de> 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 d23cc8e0e510..2ea3a4336351 100644 --- a/winsup/cygwin/mm/shared.cc +++ b/winsup/cygwin/mm/shared.cc @@ -184,25 +184,21 @@ 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);
reply other threads:[~2023-01-18 19:35 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20230118193509.DC3F43858D28@sourceware.org \ --to=corinna@sourceware.org \ --cc=cygwin-cvs@sourceware.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).