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Corinna Vinschen 63b503916d Cygwin: tls_pathbuf: Use Windows heap
Rather than using malloc/free for the buffers, we're now using
HeapAlloc/HeapFree on a HEAP_NO_SERIALIZE heap created for this
thread.

Advantages:
- Less contention. Our malloc/free doesn't scale well in
  multithreaded scenarios
- Even faster heap allocation by using a non serialized heap.
- Internal, local, temporary data not cluttering the user heap.
- Internal, local, temporary data not copied over to child process
  at fork().

Disadvantage:
- A forked process has to start allocating temporary buffers from
  scratch.  However, this should be alleviated by the fact that
  buffer allocation usually reaches its peak very early in process
  runtime, so the longer the proceess runs, the less buffers have
  to allocated, and, only few processes don't exec after fork
  anyway.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
2022-08-23 12:09:44 +02:00

57 lines
1.5 KiB
C++

/* tls_pbuf.cc
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#include <winsup.h>
#include <malloc.h>
#include "tls_pbuf.h"
#define tls_pbuf _my_tls.locals.pathbufs
void
tls_pathbuf::create ()
{
tls_heap = HeapCreate (HEAP_NO_SERIALIZE | HEAP_GENERATE_EXCEPTIONS,
NT_MAX_PATH * sizeof (WCHAR) * 10, /* 640K */
NT_MAX_PATH * TP_NUM_C_BUFS /* 4.6M */
+ NT_MAX_PATH * TP_NUM_W_BUFS * sizeof (WCHAR));
}
void
tls_pathbuf::destroy ()
{
if (tls_heap)
HeapDestroy (tls_heap);
}
char *
tmp_pathbuf::c_get ()
{
if (!tls_pbuf.tls_heap)
tls_pbuf.create ();
if (tls_pbuf.c_cnt >= TP_NUM_C_BUFS)
api_fatal ("Internal error: TP_NUM_C_BUFS too small: %u", TP_NUM_C_BUFS);
if (!tls_pbuf.c_buf[tls_pbuf.c_cnt]
&& !(tls_pbuf.c_buf[tls_pbuf.c_cnt]
= (char *) HeapAlloc (tls_pbuf.tls_heap, 0, NT_MAX_PATH)))
api_fatal ("Internal error: Out of memory for new path buf.");
return tls_pbuf.c_buf[tls_pbuf.c_cnt++];
}
PWCHAR
tmp_pathbuf::w_get ()
{
if (!tls_pbuf.tls_heap)
tls_pbuf.create ();
if (tls_pbuf.w_cnt >= TP_NUM_W_BUFS)
api_fatal ("Internal error: TP_NUM_W_BUFS too small: %u.", TP_NUM_W_BUFS);
if (!tls_pbuf.w_buf[tls_pbuf.w_cnt]
&& !(tls_pbuf.w_buf[tls_pbuf.w_cnt]
= (PWCHAR) HeapAlloc (tls_pbuf.tls_heap, 0,
NT_MAX_PATH * sizeof (WCHAR))))
api_fatal ("Internal error: Out of memory for new wide path buf.");
return tls_pbuf.w_buf[tls_pbuf.w_cnt++];
}