*c = pageCache{}
}

// allocToCache acquires a pageCachePages-aligned chunk of free pages which
// may not be contiguous, and returns a pageCache structure which owns the
// chunk.
//
// p.mheapLock must be held.
//
// Must run on the system stack because p.mheapLock must be held.
//
//go:systemstack
func (p *pageAlloc) allocToCache() pageCache {
	assertLockHeld(p.mheapLock)

		v := v
		t.Run(name, func(t *testing.T) {
			b := NewPageAlloc(v.beforeAlloc, v.beforeScav)
			defer FreePageAlloc(b)

			for _, expect := range v.hits {
				checkPageCache(t, b.AllocToCache(), expect)
				if t.Failed() {
					return
				}
			}
			want := NewPageAlloc(v.afterAlloc, v.afterScav)
			defer FreePageAlloc(want)

			checkPageAlloc(t, want, b)
		})
	}

		unlock(pp.mheapLock)
	})
	return addr, scav
}
func (p *PageAlloc) AllocToCache() PageCache {
	pp := (*pageAlloc)(p)

	var c PageCache
	systemstack(func() {
		// None of the tests need any higher-level locking, so we just
		// take the lock internally.
		lock(pp.mheapLock)
		c = PageCache(pp.allocToCache())
		unlock(pp.mheapLock)
	})
	return c
}

	pp := gp.m.p.ptr()
	if !needPhysPageAlign && pp != nil && npages < pageCachePages/4 {
		c := &pp.pcache

		// If the cache is empty, refill it.
		if c.empty() {
			lock(&h.lock)
			*c = h.pages.allocToCache()
			unlock(&h.lock)
		}

		// Try to allocate from the cache.
		base, scav = c.alloc(npages)
		if base != 0 {
			s = h.tryAllocMSpan()
			if s != nil {
				goto HaveSpan
			}