1 files changed, 19 insertions, 3 deletions
diff --git a/lib/pure/ioselects/ioselectors_epoll.nim b/lib/pure/ioselects/ioselectors_epoll.nim
index 16d901ff0..ffd60120e 100644
--- a/lib/pure/ioselects/ioselectors_epoll.nim
+++ b/lib/pure/ioselects/ioselectors_epoll.nim
@@ -53,6 +53,7 @@ when hasThreadSupport:
     SelectorImpl[T] = object
       epollFD: cint
       maxFD: int
+      numFD: int
       fds: ptr SharedArray[SelectorKey[T]]
       count: int
     Selector*[T] = ptr SelectorImpl[T]
@@ -61,6 +62,7 @@ else:
     SelectorImpl[T] = object
       epollFD: cint
       maxFD: int
+      numFD: int
       fds: seq[SelectorKey[T]]
       count: int
     Selector*[T] = ref SelectorImpl[T]
@@ -76,6 +78,8 @@ proc newSelector*[T](): Selector[T] =
     raiseOsError(osLastError())
   var maxFD = int(a.rlim_max)
   doAssert(maxFD > 0)
+  # Start with a reasonable size, checkFd() will grow this on demand
+  const numFD = 1024
 
   var epollFD = epoll_create(MAX_EPOLL_EVENTS)
   if epollFD < 0:
@@ -85,14 +89,16 @@ proc newSelector*[T](): Selector[T] =
     result = cast[Selector[T]](allocShared0(sizeof(SelectorImpl[T])))
     result.epollFD = epollFD
     result.maxFD = maxFD
-    result.fds = allocSharedArray[SelectorKey[T]](maxFD)
+    result.numFD = numFD
+    result.fds = allocSharedArray[SelectorKey[T]](numFD)
   else:
     result = Selector[T]()
     result.epollFD = epollFD
     result.maxFD = maxFD
-    result.fds = newSeq[SelectorKey[T]](maxFD)
+    result.numFD = numFD
+    result.fds = newSeq[SelectorKey[T]](numFD)
 
-  for i in 0 ..< maxFD:
+  for i in 0 ..< numFD:
     result.fds[i].ident = InvalidIdent
 
 proc close*[T](s: Selector[T]) =
@@ -127,6 +133,16 @@ template checkFd(s, f) =
   # FD if there is too many. -- DP
   if f >= s.maxFD:
     raiseIOSelectorsError("Maximum number of descriptors is exhausted!")
+  if f >= s.numFD:
+    var numFD = s.numFD
+    while numFD <= f: numFD *= 2
+    when hasThreadSupport:
+      s.fds = reallocSharedArray(s.fds, numFD)
+    else:
+      s.fds.setLen(numFD)
+    for i in s.numFD ..< numFD:
+      s.fds[i].ident = InvalidIdent
+    s.numFD = numFD
 
 proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
                         events: set[Event], data: T) =